NEW YORK -- Nestor Cortes was slated to start Wednesday against the Baltimore Orioles as the New York Yankees look to clinch the AL East title with a win. Instead, the left-hander will undergo an MRI on his elbow, according to two people with knowledge of the situation.

It's an alarming development 10 days before the Yankees are scheduled to begin postseason play.

The Yankees could turn to Marcus Stroman, who recently shifted to the bullpen, or Cody Poteet to start in Cortes' place Wednesday. Stroman last pitched eight days ago, throwing three innings in his first and only relief appearance this season. The Yankees would need to create a spot on the active roster for Poteet, who was recently activated from the 60-day injured list and sent to Triple-A.

Cortes' recent performance did not suggest he's been dealing with any elbow trouble. Beginning with a brief demotion to reliever, Cortes has given up one run with 18 strikeouts in 15 innings over his past three outings.

The stretch began with Cortes tossing 4 hitless innings in his first relief appearance of the season against the Chicago Cubs -- and afterward sharing his frustration with moving to the bullpen. He returned to the rotation five days later, limiting the Boston Red Sox to one run with nine strikeouts across five innings. On Sept. 18, he held the Seattle Mariners to four hits over six scoreless innings.

Cortes, 29, has a 3.77 ERA across a team-leading 174 innings pitched. He has made 30 starts but is expected to return to the bullpen for the playoffs.

The Yankees have, for the most part, benefited from good injury luck in recent weeks. Clarke Schmidt, Anthony Rizzo, Jon Berti, Ian Hamilton and Luis Gil also have been reinstated from the injured list since Sept. 1. The reinforcements made the Yankees more whole than just about any other club in baseball.

It also gave the Yankees a problem teams would love to have down the stretch: Six healthy capable starting pitchers for five spots. The surplus prompted the Yankees to move Cortes to the bullpen for one rotation turn before switching Stroman with him for the past two turns.

Now that surplus might take a hit.