"You'll be laying in bed and you think about that 2 1/2 footer you missed and [how] it could have changed your life. I wake up in a cold sweat sometimes."

After 36 holes Zach Johnson bagman Damon Green remains 4-under in the U.S. Senior Open and on the edge of the top 10, setting up a possible weekend run after a similar hot start in the Senior Open Championship at Walton Heath. 

Bill Fields scouted out Green's play on Thursday.

A powerful hitter who used a belly putter to good effect in the first round at Inverness (27 putts) and also made an eagle-3 on the 511-yard fourth hole (his 13th), Green's education as a golfer accelerated after he put Hoch's bag over his shoulder.

"I'm way better," Green said. "I've won like 71 tournaments on the mini-tours, but I really didn't know what I was doing til I started caddieing for Scott Hoch. He taught me a lot about course management and [I] figured you don't have to shoot at every pin. Sometimes, par's not bad. I was a better player after two or three years caddieing for Scott. I just got caught up in the caddieing business, and I made a pretty good living doing that."

One of nine children, Green was captain of the golf team at Centenary College. While he won over and over in golf's minor leagues, he never made it to the PGA Tour. His disappointing bogey on the 108th hole at Greenlefe Resort's West course in Haines City, Fla., at Q school 17 years ago cost him his card by a shot -- the closest he ever got.