An MRI on Schanuel's left ankle revealed tendinitis, Rhett Bollinger of MLB.com reports.
Schanuel's ankle has been bothering him off and on since early April, but it flared up on him recently, leading to a trip to the 10-day injured list. The first baseman isn't sure at this point how long he might be sidelined, but it appears likely to be longer than a minimum absence. Vaughn Grissom is filling in at first base for the Angels while Schanuel recovers.