CHICAGO -- The first quarter of the 2018 season has featured the Indians and Twins jousting for the top spot in the American League Central, as many expected. No team in the division having a record above .500 is more of a surprise.
Let's also not forget a rebuilding Tigers squad sneaking into early contention behind mediocre starts from the division favorites. Here's what we know overall about the five AL Central squads at the season's quarter mark.
INDIANS
One thing we learned in the first quarter: The Tribe bullpen looks like a weakness. After having longtime setup man Bryan Shaw depart via free agency, Cleveland knew there would be a ripple effect throughout the relief roles. The Indians didn't expect things to get this bad, though. Through 40 games, the club's 5.45 bullpen ERA ranked 28th in the Majors.
What we'll be watching in the second quarter: On the positive side, fans will be watching to see if Jose Ramirez and Francisco Lindor -- who both finished in the top five in AL MVP voting last year -- can actually get better. They've again been one of the game's most dynamic duos. On the other side, the next quarter will show if players like Jason Kipnis and Edwin Encarnacion can pull out of their extreme cold spells.

Key series or stretch of schedule: From May 18-27, the Indians will play nine games against the last two World Series champions. The seven games against the Astros, plus a two-game set on the road against the Cubs, will provide a good litmus test for the Tribe.
Stock watch: The Indians' stock is down right now. The team entered with extremely high expectations and has hovered around the .500 mark. They remain the division favorites, but the Tribe has plenty of kinks to iron out.
ROYALS
One thing we learned in the first quarter: The Royals aren't very good without All-Star and Gold Glove catcher Salvador Perez. With Perez on the disabled list, the Royals lost 15 of the first 20 games to open the season. They've been closer to who they're expected to be with him because of his presence in the offense and behind the plate.

What we'll be watching in the second quarter: Left-hander Danny Duffy. The Royals received plenty of offers for Duffy during the offseason but held off dealing him, either because they didn't like the return or because they consider him part of the future for when they complete their next rebuild. But Duffy is going through perhaps the worst stretch of his career; he's 1-5 with a 6.51 ERA. Duffy and the Royals say he's 100 percent and just in a slump. Duffy's value at the Trade Deadline could hinge on his second-quarter starts.
Key series or stretch of schedule: Near the end of June, the Royals will embark on a four-city road trip that starts in Houston for three games, returns to Kansas City for a makeup game against the Angels, resumes in Milwaukee for two and then concludes in Seattle for three. All four of those teams are either in first place or contending. That trip will test the Royals' character, especially if they continue to fade in the Central.
Stock watch: This team wasn't really designed with postseason intentions, but it shouldn't be this bad, either, so let's say its stock is down. This season is about the MLB Draft in June, flipping some veterans at the Trade Deadline to further restock the farm system, and getting some younger players (Brad Keller, Tim Hill, Jakob Junis, Jorge Soler, Cheslor Cuthbert) some valuable experience.
TIGERS
One thing we learned in the first quarter: The Tigers have taken on some of the characteristics of Ron Gardenhire's previous team, notably a more aggressive baserunning style and a willingness to compete until the final out. Their four walk-off wins are the most by a Tigers club through 40 games since 1993. Their baserunning has been epitomized by JaCoby Jones, who scored from first base on a single Saturday.
What we'll be watching in the second quarter: Can Matthew Boyd keep up his strong pitching? The left-hander quietly has become a front-line starter in the Tigers' rotation, averaging six innings per outing and tossing six or more innings of one-run ball in four of his first five starts. He has pitched deeper into games and drastically reduced his home-run rate by taking something off his fastball and improving his slider, allowing a .244 BABIP. If he can continue this stinginess as the weather warms up, the Tigers have a better rotation beyond Michael Fulmer.

Key series or stretch of schedule: The Tigers will play 18 games in a 17-day stretch from Memorial Day weekend into mid-June, thanks in part to a makeup doubleheader against the Yankees on June 4. Besides the Bronx Bombers, the stretch includes four games against the Angels and three-game sets against the Blue Jays, Red Sox and Indians.
Stock watch: It's steady. Everybody in Detroit knew this was a rebuilding season, so their record is no surprise. What has impressed has been the way they've competed. This is an entertaining team to watch, even if the results don't show it.
TWINS
One thing we learned in the first quarter: The Twins have had their depth tested with injuries to key players such as Ervin Santana, Byron Buxton, Miguel Sano and Jason Castro, but they've started to play better after a rough stretch that saw them lose 12 of 14. Eduardo Escobar's production has been key, while Eddie Rosario has heated up and the pitching has been steadier.

What we'll be watching in the second quarter: Buxton returned from the disabled list but has been a bit rusty so far, as he skipped a rehab assignment because his defense is so important to the team. If he can get it going offensively, it would be a major boost to the lineup. Right-hander Lance Lynn also must get it going after struggling so far and must get his command back on track.
Key series or stretch of schedule: May 31-June 10. The Twins have an 11-game homestand to try to make up ground, including a four-game series against the Indians from May 31-June 3. They follow that with a four-game series against the White Sox that includes a doubleheader before hosting the Angels for a three-game set.
Stock watch: Up. In fact, they've won 8 of 12 games.
WHITE SOX
One thing we learned in the first quarter: Year 2 of the rebuild, tabbed as development-focused, has been the toughest part to date, as mentioned a few times previously by general manager Rick Hahn. There's talent in place at the big league level, but there have been noticeable growing pains for top young pitchers such as Lucas Giolito, Carson Fulmer and even Reynaldo Lopez. The same held true for second baseman Yoan Moncada, who has steadied things after a slow start and become one of the team's more consistent offensive performers.

What we'll be watching in the second quarter: Does Michael Kopech arrive? The right-hander ranks No. 2 among White Sox prospects and No. 9 overall per MLB Pipeline, possessing elite stuff, but he has struggled with command over his last two starts. Hahn will not rush Kopech or outfielder Eloy Jimenez, who is currently crushing the ball for Double-A Birmingham and is the organization's top prospect (No. 3 overall) or any other top prospect before that player checks off every box needed for promotion.
Key series or stretch of schedule: From May 28 to June 20, the White Sox play 20 of their 23 games against teams considered playoff contenders and three against a competitive Detroit team. That stretch includes 10 against the Indians and four against the Twins.
Stock watch: It would be easy to say it's way down considering the White Sox have won two series all season, have the worst record in baseball and have simply not played good fundamental baseball. But perspective is also needed to understand this team is building more for the future than success in the present. So a qualified steady or slightly down might be a more accurate read, as it's really about individual growth as opposed to team wins and losses.