After Monday's 8-1 win over the Tampa Bay Rays, the Yankees announced Sanchez was diagnosed with a Grade 1 strain of the right brachialis muscle. He is expected to miss at least four weeks.
"Forgive me (for) not knowing the name of the muscle, it's behind the bicep," Yankees manager Joe Girardi said. "I don't know the name of it but they're thinking four weeks. He's going to be out four weeks."
"At the beginning, it was supposed to be 10 days," Sanchez said through a translator. "After the test results, the doctor recommended about four weeks. So that's what we're going with."
Sanchez was originally diagnosed with a strained right biceps after leaving Saturday's game in Baltimore. He was placed on the 10-day disabled list Sunday and introduced to the crowd as part of the opening day ceremonies before going for an MRI exam.
"I was mentally prepared for anything," Sanchez said. "That's the time they tell me, so we just got to wait and see."
Sanchez will not participate in any baseball activities for at least 10 days and then the Yankees will plan the next step barring any setbacks.
Sanchez was off to a 3-for-20 start after hitting .299 with 20 home runs and 42 RBIs in 53 games last season. He placed second in the AL Rookie of the Year voting behind Detroit right-hander Michael Fulmer and then hit .373 with five home runs and 16 RBIs during spring training.