Teheran exited Friday's game against the Phillies with right upper back tightness.
Teheran struggled through three innings Friday, allowing three earned runs on two walks and two hits with two strikeouts. More cause for concern is the fact that the right-hander's fastball topped out at 87.5 mph, when the pitch usual sits in the low-90s, David O'Brien of The Atlanta Journal-Constitution reports. The severity of the injury is unknown at this point, but more information should become available as the 27-year-old is further evaluated.