The Marlins say Thursday they plan to put Kotchman on the DL on Friday, and make a corresponding roster move then.
Kotchman clutched the back of his leg while running out a double-play grounder in Miami's 3-0 loss at the Washington Nationals on Wednesday.
Kotchman says he "heard a pop" on the play.
Manager Mike Redmond says he'll have "a little bit of a tryout over at first base, trying to figure out who's going to fill in."
Gregg Dobbs was in the lineup playing first base and batting fourth Thursday against Washington. Redmond mentioned Austin Kearns, Chris Valaika and even catcher Miguel Olivo as possible replacements at first.