Now past the midway point of June, the top dogs of the MLB have, for the most part, emerged. But even in their success, there's still plenty of baseball left to play, and there are still concerns that could be these division leaders' undoings down the stretch. Let's identify the most glaring red flag for baseball's six first-place teams.

1. Yankees: Luis Severino's Injury

Tampa Bay Rays v New York Yankees

For all of the Yankees' success in the face of key injuries, they aren't going to get very far in the postseason without ace Luis Severino. He's yet to pitch in a game this year due to a rotator cuff injury, and isn't expected back until the middle of July at the earliest. If he doesn't come back healthy and ready to go, the Yanks will be in serious need of rotation help.

2. Twins: Bullpen

Minnesota Twins v Cleveland Indians

If there's one weak spot for the Minnesota Twins, it's their bullpen. The relief corps sports a middling 4.58 ERA, and there's not much help to look to in the farm system. Recent playoffs have shown the importance of having reliable relievers, something the Twins really don't have. Addressing the pen should be their primary concern moving forward.

3. Astros: Middle Infield Health

Minnesota Twins v Houston Astros

The Astros don't have that many areas of concern considering just how deep they are, but the health of their middle infielders has been a problem in 2019. Stars Jose Altuve and Carlos Correa have both struggled with injuries this year; Houston's lineup just isn't the same without the two of them doing their thing.

4. Braves: Starting Pitching

Philadelphia Phillies v Atlanta Braves

The addition of Dallas Keuchel helps the Braves tremendously, but half a season from one man can only do so much. Kevin Gausman sports an ERA of 6.21 and Mike Foltynewicz hasn't found his 2018 All-Star form, posting a 5.53 ERA of his own. If anything will be Atlanta's undoing, it will be the starters.

5. Cubs: Closer

Chicago Cubs v Colorado Rockies

The Cubs have four separate relievers with multiple blown saves and eight with at least one. Steve Cishek sports an ERA of 6.14 since May 24 and Pedro Strop has been incredibly inconsistent. Chicago just hasn't been able to slam the door this year. They'd better hope Craig Kimbrel can remedy the situation.

6. Dodgers: Catcher

Chicago Cubs v Los Angeles Dodgers

Perhaps the only flaw the Dodgers have sits behind the plate. After losing Yasmani Grandal in free agency, they've been unable to squeeze offensive production out of their backstops. Their catchers' combined 86 wRC+ ranks 18th in the MLB, creating an offensive hole in an otherwise sweet-swinging lineup.