New York Yankees ace right-hander Gerrit Cole is undergoing diagnostic tests on his throwing elbow, MLB Network reported on Friday.

The six-time All-Star missed the first few months of the season with elbow soreness, then finished 8-5 in 17 starts with 3.41 ERA, 1.126 WHIP and 99 strikeouts over 95 innings. He made five postseason starts, going 1-0 with 2.17 ERA over 12 2/3 innings.

Cole struggled in his spring training outing on Thursday against the Minnesota Twins, surrendering six runs in 2 2/3 innings.

The extent of Cole’s injury is unclear.

Losing Cole would be a crucial blow for the Yankees, who have World Series aspirations. Fellow starter Luis Gil, the reigning American League Rookie of the Year, is expected to miss at least three months with a lat strain.

Potential trade candidate Marcus Stroman suddenly appears to be an important piece of the roster. He would easily slide back into the rotation, alongside Max Fried, Carlos Rodon and Clarke Schmidt.

Stroman was left off the Yankees’ AL Division Series roster, and Fried’s signing added more uncertainty to his role. Nevertheless, the veteran right-hander was a solid performer last season. In 30 games, he recorded a 4.31 ERA, 113 strikeouts and 0.7 WAR.

–Field Level Media