Jordan Spieth soared up the Sawgrass leaderboard and revealed it was a serving US Marine who had inadvertently spared him a possible missed cut at The Players Championship.

Spieth was five over for his second round on Friday heading to the 18th hole, where a wild drive looked set to find the water and leave him in even deeper trouble.

Already on the cut borderline at two over, Spieth got a lucky break when the stray tee shot struck a spectator's knee, and bounced not into the drink but back onto the fairway.

He was gifted a reprieve, played his second shot just short of the green and then chipped in for an eagle to get back to level par through 36 holes.

Following that with a six-under 66 on Saturday to move two shots outside the top 10 gave Spieth hope of figuring even higher on the leaderboard on Sunday.

"Especially with the way my round finished yesterday I have nothing to lose, I have everything to gain," Spieth said.

Addressing Friday's lucky break, Spieth was asked whether he had since made contact with the man whose knee felt the full force of his ball.

"He's over there right now," Spieth said. "He's an active Marine. His name is Matt. He didn't want anything."

Spieth added: "I spent a little time with him yesterday. He didn't want anything, but I thought if I could do anything for him, I'd try to, and the [PGA] Tour stepped in and hooked him up too.

"So hopefully he's having a good weekend. And his knee, I mean, once I found out he was an active Marine I don't really think getting hit in the knee really does much to those guys.

"I would like to say once the cut moved to two over I felt like I could have still finagled my way through. But it's still two shots that it saved me at least. That will make a difference regardless tomorrow."