The Washington Nationals and Baltimore Orioles were the first teams in the MLB to clinch their divisions last night, and now their managers are likely thinking ahead to the postseason. These two teams have interesting pitching personnel, but one starter will be left out of the playoff rotation.

The biggest question mark perhaps lies in Washington: Who will be the starting four once October rolls around? Well, it's certainly a tough decision since Stephen Strasburg (3.34 ERA), Jordan Zimmermann (2.83 ERA), Gio Gonzalez (3.79 ERA), Doug Fister (2.55 ERA) and Tanner Roark (2.85 ERA) have all had exceptional seasons in the rotation. However, Roark has already eclipsed his career-high total for innings pitched in a season and has by far the least major league experience (35 starts career starts), which could make the choice obvious.

But he's been very consistent all year and the Nationals might not want to take him out of his groove. After all, he could be a lucky charm after dominating the Braves on Tuesday night to help the Nats clinch the NL East. Fister by far has the most playoff pitching experience with seven starts, and Gonzalez is next with two, followed by Zimmermann with only one. Strasburg and Roark have never pitched in the postseason. ESPN's Buster Olney speculates Washington might consider using Strasburg or Gonzalez out of the bullpen. Strasburg has been erratic at times this season (four or more earned runs in eight starts this year, five of which have been losses), while Gonzalez has had great success against lefty hitters this year (just one home run surrendered in 2014). Strasburg in short-term relief could be dominant and Gonzalez can be used to face lefties in crucial situations. However, it could be Roark who gets sent to the bullpen after all because of his overall inexperience.

In Baltimore, the Orioles have already amassed 91 wins with no clear cut ace. Of those in the rotation at some point this season, Miguel Gonzalez (3.28 ERA in 2014) and Wei-Yin Chen (3.58 ERA) have only one postseason start, while Ubaldo Jimenez (4.90 ERA), who the team has moved in and out of the rotation this season, have five career postseason starts with a 3.54 ERA (all with the Colorado Rockies). Prior to clinching last night, Buck Showalter was asked about it, but didn't give much information.

"We have a lot of options," Showalter said in this CSN Baltimore article. "But right now we're trying to get into the playoffs. Once we're able to do that, we'll address more of that. It is smart to kind of look at it so you don't get caught."

Chris Tillman (12-5 with a 3.29 ERA), Bud Norris (13-8 with a 3.74 ERA) and Kevin Gausman (7-7 with a 3.57 ERA) all remain solid options as well. Showalter might have a difficult time deciding before the postseason officially begins on September 30.

Check out Bleacher Report's postseason roster predictions.