Chicago Cubs pitcher Carlos Zambrano's MRI on Monday revealed that the hurler has "tennis elbow". However, Zambrano is unsure yet if he will miss his next start until he throws on the side. Zambrano, who was pulled after 3 1/3 innings on Saturday against Washington due to tightness in his right forearm, is scheduled to start Friday against the crosstown-rival White Sox. "Carlos is pretty anxious to get right after it," said Cubs trainer Mark O'Neal. "The plan now is try to do a side session on Wednesday and go from there." Zambrano, 23, currently sports a 3-2 record with a 4.09 ERA this season.