Matt Harvey is battling a blister on his right index finger that could cost him his final start before the All-Star break, Mets manager Terry Collins revealed Tuesday morning.

"We're probably going to back him off or not have him pitch, one or the other," Collins said after the Mets' 4-3 victory over the Giants in 16 innings.

How a missed start in Pittsburgh on Saturday would affect Harvey's availability for next Tuesday's All-Star game at Citi Field is unclear.

"Whatever they decide is their call and I'm going to prepare like I have a start [Saturday]," Harvey said. "Whatever they tell me is the way it goes."

Harvey said the blister has been present for his last three starts and affected his grip.

"It's no excuse for my poor pitching," Harvey said after allowing three earned runs over seven innings against the Giants. "I feel fine with it, so I've just got to figure some things out and get back out there."