The Red Sox announced why rookie outfielder Roman Anthony was removed from the starting lineup just minutes before opening a series with Kansas City.

Roman Anthony — who was originally slated to bat third in Boston’s lineup on Monday as the team’s right fielder — was scratched just before the start of the game. Boston later announced that the promising rookie outfielder was taken out of action due to “mid-back tightness.”

Anthony was scratched due to “mid-back tightness,” according to the Red Sox. NESN cameras caught Anthony looking uncomfortable during pregame warm-ups on the Fenway Park field.