David Robertson injured his left foot after stumbling on a flight of stairs at his home Wednesday while moving some empty boxes. Yankees manager Joe Girardi admitted "some cause for concern" after the right-hander underwent an MRI. Robertson has been sent back to a Tampa hospital for further tests. "I'm not gonna speculate on what he has," Girardi said. "We're not sure what's going on. I'm sure we'll have a better idea [Friday]." Robertson underwent a weight-bearing X-ray and a CAT-scan on the affected area of his foot and that the results would be overnighted to New York.