He will undergo imaging, according to the team.
LeMahieu whiffed on a pitch from Nathan Eovaldi in the fourth inning, followed through awkwardly and began to favor his left hand. LeMahieu paced around the plate area, followed by a team trainer and manager Aaron Boone, but remained in the game.
LeMahieu’s average dropped to .411 when he grounded out weakly to shortstop. Boone again visited with him on the field between innings, and LeMahieu took his position at second base for the top of the fifth inning.
Tyler Wade replaced LeMahieu at second base to begin the sixth.
LeMahieu, a three-time Gold Glove winner, hit .327 last season. He is vying to become the first player to win batting titles in both leagues. He took the NL crown with Colorado in 2016, when he hit .348.
The Yankees are already without star sluggers Aaron Judge and Giancarlo Stanton, both on the injured list. Judge has a strained right calf and was put on the IL on Friday, while Stanton is out for three to four weeks with a strained hamstring.
The Associated Press contributed to this report.