Chase Headley thought his 2007 season was over. A top prospect in the San Diego Padres organization, Headley flourished in Double-A that year, winning Texas League Player of the Year honors and leading the San Antonio Missions to the league championship. He also got a taste of the Big Leagues, a short 12-day spell when Padres starting third baseman Kevin Kouzmanoff got hurt in June. But Headley wasn't initially recalled when rosters expanded from 25 to 40 active players on Sept. 1.
And so even with the Padres embroiled in a heated pennant race, Headley retreated to his Knoxville, Tenn., home after the Missions' season ended on Sept. 15. "I was completely in shutdown mode," he recalls.
Headley's sabbatical ended 10 days later, after Padres outfielder Mike Cameron tore a ligament in his thumb diving for a ball and fellow outfielder Milton Bradley tore his ACL during an argument with first base umpire Mike Winters. With the Padres needing reinforcements, Headley was back in the Big Leagues.

A lot had changed since June, Headley noticed. The intensity was similar -- Big Leaguers take the game just as seriously in June as they do in September, he says -- but, with the postseason nearing, every pitch and every at-bat carried a heightened sense of urgency for his teammates. Headley, meanwhile, felt like an interloper in the clubhouse. He was buried on the bench and didn't even take batting practice on the field, so as not to disrupt the routine of the regulars.
Such is life for the September call-up.
"I didn't feel like I was as invested as those guys were," he says. "These are the guys that had been here all year fighting. I didn't expect to play, so I was kind of soaking it all in, trying to learn, trying to absorb as much as I could, and staying out of the way, to be honest. You don't want to mess up anything that they have going on. That's the tricky thing about September."
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Let us count the ways September baseball is tricky -- tricky for ballplayers, managers and the front office. For the first five months of the season, each team has a 25-man active roster composed of players from its 40-man roster. Then, on Sept. 1, just as the postseason chase enters its final heat, the rules change: Rosters expand, allowing a team to activate and play anyone from the 40-man.
The roster, in turn, becomes flooded with bullpen arms -- long relievers, situational relievers, mop-up guys -- and position players, all of whom loom as potential pinch-runners, pinch-hitters and defensive replacements. This changes how the game is played and managed, which, according to some critics, compromises the integrity of the game. But the system, which has existed for decades, benefits young ballplayers in many ways.
Yankees legend Jorge Posada says his stint as a September call-up aided his development. Along with Derek Jeter and Ruben Rivera, Posada was promoted to the Big Leagues in late 1995; Jeter's September call-up followed a short stint in the Majors earlier in the year. A 24th-round draft pick who converted from the infield to catcher in the Minors, Posada was a raw prospect, and even with starting catcher Mike Stanley an impending free agent, Posada wasn't considered the Yankees' catcher of the future in 1995. He was the catcher of the distant future, the guy who would eventually replace the guy who replaced Stanley; Posada finally became the Yankees' primary starting catcher in 1998.
With the Yankees battling for a Wild Card berth until the final day of the 1995 season, the rookies didn't receive much playing time; Posada's only action came as a defensive replacement in the ninth inning of a game on Sept. 4. But he saw first-hand what went into being a Big Leaguer.
"You learn in the Minor Leagues, but to be around the older guys -- the Wade Boggses, the O'Neills -- and see their preparation and intensity, it's just a different story," Posada says. He also cites Stanley, a 10-year veteran who buried himself in scouting reports and paperwork before each game, and, of course, the Yankees' captain, as paragons. "The thing I remember most was Don Mattingly. Growing up, I was a big, big fan of Mr. Mattingly. I was just in awe of his preparation, his work ethic and everything he did to put that team in the playoffs."
Despite the slight résumé, Posada was named to the Yankees' 25-man playoff roster before their AL Division Series matchup against the Seattle Mariners. And although he was a bit player during the epic tussle that came down to extra innings in a deciding Game 5 -- pinch- running in the bottom of the 12th inning of Game 2 -- Posada, who would eventually win five World Series rings, reveled in the experience. "I learned so much that year," he says. "[The Seattle series] taught us a lot. It taught us that you can't take things for granted."
Like many September call-ups on contending teams, Posada barely cracked the lineup, but there are ways rookies can benefit from just being around the club. A September call-up learns how to deal with the media; gets accustomed to Big League clubhouses and to the intensity of games played before raucous crowds; observes opposing pitchers and hitters in person; receives coaching from Major League instructors; and sees tricks of the trade from veterans that eventually become part of their own routine.
One of the biggest adjustments for young players is sifting through the proliferation of data (both statistical and video) that Major League teams rely on. When Gary Sanchez was promoted from Scranton/Wilkes-Barre in late 2015, and then again in May and in August 2016, he shadowed then-Yankees catcher Brian McCann to learn as much as he could about playing the position in the Big Leagues. He also gained access to meticulous scouting reports.

"There is more information in the Big Leagues than in the Minor Leagues," Sanchez said through the team's bilingual media relations coordinator, Marlon Abreu. "When they called me up, I felt ready to catch in the Big Leagues, but the one thing that I had the opportunity to learn and increase my knowledge on was the scouting reports for the teams I was going to face in the Big Leagues … I would say that's the biggest set of skills that I learned from that time."

As with many of baseball's wonderful and weird traditions, September call-ups are steeped in history. But the notion of calling up prospects on or after Sept. 1 solely to get them acclimated to the Big Leagues is dying out. Back in the 1950s and 1960s, teams hesitated promoting players for budget reasons -- more players meant more money spent on salary, food, travel and hotels. Nowadays, financial concerns revolve around managing service time in order to stave off arbitration and potentially free agency.
With the stakes so high, a September call-up is no longer dangled as a reward for a good season in the Minors. The player must be able to contribute to the Big League club, says Yankees general manager Brian Cashman. "We're not going to add somebody and give them Major League rate of pay and service time and give all that stuff away if there's not value that we can cash in on for the present."
Cashman begins contemplating call-ups about a week before Sept. 1. After meeting with manager Joe Girardi and bench coach Rob Thomson to discuss the team's needs, he then huddles with his baseball operations staff before deciding. There are many variables involved: the age of the roster; how the roster is constructed; and whether a top prospect is blocked at a position -- a young player might not benefit from playing just once or twice a week.
One thing Cashman doesn't take into consideration is the impact call-ups will have on Minor League pennant races. "It's inconsequential," he says. "I raided Scranton last year, and they wound up winning the whole thing regardless. I traded the International League MVP Ben Gamel to Seattle. I promoted everybody and anybody after it was all said and done. Unfortunately, nobody ever truly remembers who winds up winning what in the Minor Leagues. It's really about best serving the Major League club."
Cashman is eager to dispel another myth about September call-ups -- that it's a good indicator of future performance at the Big League level. "No. There are guys up who aren't typically Major Leaguers. It's an extension of Triple-A in some cases depending on who you're playing," he says. "So you have to temper whatever you see in September and measure the performance level [against] the broader context of how they were performing at the lower level."
Take former Yankees top prospect Jesus Montero, for example. A slugging catcher from Venezuela, Montero was one of the most anticipated September call-ups in recent Yankees history when he debuted in September 2011. At first, he lived up to the hype, slashing .328/.406/.590 with four home runs in 61 at-bats. A closer look reveals that he didn't benefit from facing so-called Quadruple-A pitching, either; Montero homered off Jim Johnson twice and once apiece off Jered Weaver and Junichi Tazawa, all major league stalwarts. He also went 2 for 2 in Game 4 of the ALDS against the Detroit Tigers.
Despite the impressive debut, Cashman traded Montero that offseason to the Mariners for starting pitcher Michael Pineda. Would Seattle have surrendered Pineda -- at the time one of the most coveted young arms in baseball -- if not for Montero's performance in September and October?
"It's hard to speak for another club. It didn't hurt, no doubt," Cashman says. "I mean, we were high on [Montero] already, but I think Seattle's interest piqued even further from that." Montero batted .260 in 135 games for Seattle in 2012 but was a nonfactor thereafter.

When discussing the benefits of September call-ups, Cashman cites the fact that expanded rosters give managers more flexibility. Girardi could do without it. "I think it becomes more difficult for a manager, just because of all the moves the other manager can make," Girardi says. "A team can have five lefties and six righties in their bullpen and can mix and match the whole time. As a manager, we try to look for advantages. A lot of them are taken away just because there are so many people on a roster."
With baseball becoming more and more specialized, there is already room for a lefty specialist or two out of the bullpen and a personal catcher on the 25-man roster. September baseball magnifies this growing trend. As Girardi stated, with bottomless bullpens, teams can mix and match their relievers from the early innings on. Managers can also deploy pinch-hitters and pinch-runners earlier and more often.
"That's not something you can carry [on the roster], a pinch-runner, for the first 130 games," Girardi says. In September 2015, the Yankees promoted speedster Rico Noel, who stole five bases that month despite coming to bat just twice in 15 games. "But now all of a sudden you've got a weapon and you're going to look for a spot to use that weapon, and it changes the whole complexion of the game. Again, I'm not a huge fan of it."
Girardi proposes changes to the current system: A 28-man September roster allowing the inclusion of an additional pitcher, position player and catcher. The 28-man roster is fluid and can change daily, but a starting pitcher can't pitch for 10 days if he is removed from the roster.
The Yankees' manager isn't the only member of the staff affected by the roster expansion. September call-ups need lockers, and it's up to Rob Cucuzza, the team's head equipment manager, to provide them.
Cucuzza's preparation begins in mid-August when he alerts the team's off-site storage facility to prepare to ship six to eight temporary lockers to Yankee Stadium, which will supplement the 36 permanent stalls that line the perimeter of the Yankees clubhouse. Once they are delivered, Cucuzza stows the lockers down the hall from the clubhouse. As players get called up, Cucuzza rolls them in and places the lockers adjacent to two large columns near the center of the clubhouse.
"They're actually pretty nice lockers," Cucuzza says. "When they're set up, they actually look like they belong there. So, they're not set up where the guys feel like they're sticking out somewhere or it looks like a temporary locker."
"Things get pretty crowded," Brett Gardner says. "It looks a little different, but it's an exciting time."
For Cucuzza, the only other challenge involves adjusting the amount of food he orders for the players. "We deal with expanded rosters in spring training for almost two months," he says. "That's 65-70 players for six, seven weeks. So, 40 is nothing for us."
***
Headley's September call-up ended in heartbreak when the Padres lost a Wild Card tiebreaker game in extra innings against Matthew Holliday and the Colorado Rockies. Despite his role as mostly a spectator after his promotion, Headley did get into Game 163. He cracked a pinch-hit single in the 13th inning after Scott Hairston's two-run home run gave the Padres a short-lived lead. Still, he remembers the game as a learning experience.
"It was a great opportunity to see the intensity and the speed of the game," he says. "I just remember the emotion of the swings that came about in that game and how the guys who had been there for a while handled it. Regardless of which way the momentum was going, those guys stayed level."
Now an 11-year veteran, Headley has a different outlook on September baseball. He recognizes its benefits: Young players gain Big League experience while cashing a couple Big League paychecks. But he wishes the games were played under the same set of rules all season. "During the season, it's always your best 25 against their best 25. Sometimes in September, it's their best 35 versus your best 28," he says. "Trying to prepare in September, I'm looking at all the bullpen arms and there are 15 guys I have to prepare for. It's impossible."

Although there were rumors that baseball was contemplating changing the September call-up system, it went untouched in the new Collective Bargaining Agreement that was ratified last December and will be in effect through the 2021 season. But maybe the whole notion of September call-ups has become antiquated, especially in a game that now, more than ever, values the contribution of young players.
In fact, in recent years, the Yankees haven't even waited until September to promote their top prospects. Greg Bird and Luis Severino debuted in the Bronx in August 2015, with Christopher Austin and Aaron Judge arriving the following August. When asked if he can remember the last time he anticipated the arrival of a September call-up, Cashman pauses for a moment. "Never in advance did I think, 'Oh, this guy's really going to help us out,'" he says. "If I felt that way, he would have been up before September."