After the play at first, McCoy returned to the mound and threw a warmup pitch but came off the field with Detroit trainer Kevin Rand immediately after.
"We'll have to figure out what we're going to do in terms of what his status is going to be," Tigers manager Brad Ausmus said. "I haven't talked to [Detroit general manager Dave Dombrowski] about it yet, but we'll make that decision here in a little bit."
According to Ausmus, McCoy felt the injury on his second step on his way to first base to try and get Zobrist. Blaine Hardy, another lefty, replaced McCoy on the mound.
Since making his Major League debut on June 22, McCoy has appeared in five games for Detroit. He holds a 1.80 ERA, having allowed just one run.
McCoy was called up from Triple-A to take the roster spot that opened when lefty Ian Krol went to the disabled list with shoulder inflammation. Krol pitched a successful inning in a rehab assignment Friday night.
Jason Beck is a reporter for MLB.com. Read Beck's Blog and follow him on Twitter @beckjason. Matt Slovin is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.