UP: David Ortiz
Ortiz missed the first 15 games of the season with a strained right Achilles tendon, but he hasn't slowed down since joining the Red Sox's lineup on April 20, helping the Sox become the eighth team since 1997 to go from worst to first in one year. It's a balanced offensive attack, but the grizzled veteran Ortiz, without a doubt, is the leader.
There are nine Red Sox who have at least 50 RBIs, led by Ortiz with 98. There are eight Boston players with at least 10 home runs, led by Ortiz with 29, and both Mike Carp and Dustin Pedroia are sitting on nine. And at .307, Ortiz is leading the Red Sox in batting average, with four other regulars batting at least .294. The result? The Sox have run away with the American League East, having taken over first place for good on May 26. Boston has spent 136 games atop the division, did not have a losing record in any month and has not lost more than three consecutive games all year.
DOWN: Yasiel Puig
The talk of the baseball world after his June callup by the Dodgers, Puig has become a virtual non-factor in September, hitting .227 with 17 strikeouts in 66 at-bats. And the Dodgers? Well, after a resurgence that saw them rally from last place in the National League West on July 1 to the division title, the Dodgers have lost 11 of their last 18 games, and they are 10-11 in September. Los Angeles ranks eighth in the NL in both average (.254) and runs scored (82), despite strong efforts from late addition Michael Young (.385) and Hanley Ramirez (.408).
Does September really matter? Since the advent of the Wild Card in 1995, only three times has a team with a losing record in the final month of the season won a World Series -- the 2006 St. Louis Cardinals (12-17), the 2000 New York Yankees (13-17) and the 1997 Florida Marlins (12-15). The past five World Series champions have finished strong, averaging 18.6 wins for the season's final month.
UP: Josh Donaldson
In 89 big league games prior to 2013, Donaldson had hit .232. Given an everyday opportunity this year, Donaldson has been a major factor in the A's claiming their second straight AL West title. Having at least 100 plate appearances at every spot in the lineup between third and sixth, Donaldson has hit .306 with a .388 on-base percentage, 24 home runs and a team-best 92 RBIs.
Since Aug. 24 -- when Oakland (22-7) has left Texas (9-18) in the AL West dust -- Donaldson has hit .363 with six home runs and 20 RBIs, joining teammates Yoenis Cespedes (22 RBIs), Brandon Moss (21) and Jed Lowrie (21) in the 20-RBI club over that 29-game stretch. Donaldson is part of a big-bang A's offense that may be eighth in the AL with a .254 season average, but ranks third in runs scored with 734.
DOWN: Adrian Beltre
Beltre has put together a solid season (.318, 28 home runs, 88 RBIs), but the Rangers have been in a September swoon, and Beltre has struggled himself. He's hit only .266 with no home runs and only six RBI while Texas has lost 15 of 20 games. Only the Chicago White Sox (5-16) have a worse record for the month.
That's why the Rangers -- who faded in the final weeks in a bid to win the AL West a year ago and then lost the AL Wild Card Game -- not only have been overtaken by the A's in the division, but suddenly find themselves behind both Tampa Bay and Cleveland in the Wild Card race. It is certainly not all Beltre's fault. Elvis Andrus (.323) is the only regular hitting better than .275, and Andrus (16) and Alex Rios (10) are the only Texas players with at least 10 RBIs this month
UP: Freddie Freeman
Atlanta's success might be driven by its pitching staff, but there has to be some run production, and Freeman has been the key to the Braves' offense. Atlanta's 3.19 ERA is the best is baseball, and its 52 saves are tied with Pittsburgh for the NL lead. Kameron Loe (0-1 as a starter) is the only one of 10 pitchers who have started a game for the Braves to have a losing record in the starting role.
Offensively? Well, the Braves rank 10th in the NL and 21st in baseball with a .248 batting average, but they do have a big-bang approach, having scored 661 runs -- fifth in the NL -- thanks in no small part to an NL-best 177 home runs. Freeman (.314) and Chris Johnson (.329) are the only Atlanta players hitting above .260. Freeman leads the Braves with a .392 on-base percentage. He also ranks second on the team with 23 home runs, three behind Justin Upton. Freeman also has 105 RBIs, the only Atlanta player with more than 67.
DOWN: Ryan Zimmerman
OK, Zimmerman has been a key part to the Nationals' late surge, but the surge will in all likelihood fall short, and a team many expected to be in the World Series will be left out of the playoffs. Zimmerman has hit .322 with 11 home runs and 16 RBIs in September, during which the Nats are 16-5. Washington, however, came into September with only a 68-67 record and too much ground to make up to earn a second consecutive postseason bid for first time in franchise history. Zimmerman hit .275 with 15 home runs and 61 RBIs in the first five months of the season.
And then there is Gio Gonzalez. The left-hander is 3-1 with a 2.36 ERA in September, but he was only 8-6 with a 3.56 ERA in the first five months of the season, a far cry from the 21 games he won a year ago when he anchored the Nationals' rotation.
Tracy Ringolsby is a columnist for MLB.com.