Coughlin didn't offer an opinion when asked if Cruz's injury was serious.
"I don't know," Coughlin told reporters. "I mean he runs to make his living. He's obviously got an issue with the heel ... and they're going to continue to do some tests on him."
Starting center David Baas also suffered an injury in the first quarter. Baas got rolled up on from behind and was seen on the sidelines being examined by trainers before heading to the locker room.
The initial read on Baas' injury is a sprained MCL, NFL.com's Ian Rapoport reported, citing a person briefed on the injury. The veteran center will have further tests on Monday.
Baas had several surgeries during the offseason, though he never offered any specifics on what was done.