The Irishman fired one under par at the Firestone Country Club in Akron, Ohio, to lie three shots behind overnight leader Retief Goosen.

Harrington said: “My brain was a bit scrambled all day and my mind was erratic.

“Thankfully I hit enough good shots to make some birdies and that was obviously important because I did some silly things focus-wise out there, hit a couple of very slack chip shots.

“The great news for me is that one under par keeps me in the tournament and I expect to get better each day and if I do manage that I expect to be well in there on Sunday.”

Harrington said he monitored his fitness levels during the week had off after winning the Open but was not expecting to be on top of his game in Akron.

He added: “It doesn’t matter how hard you’re trying but if you’re not quite with it, your mind is racing a bit out there.

“I took double bogey on my fifth hole and misjudged my chip shot by about 20 yards – I hit it well and it came up about 20 yards short of where I needed to land it.

“So things like that just happen, you’ve got to expect it to happen. When I did relax, I still hit some bad shots but at least I made some birdies.”