Phil Mickelson fired himself back into contention for his second major of the year on Friday after launching a birdie blitz on day two of the Open.

The American's hopes of adding the Claret Jug to his US Masters green jacket looked to have sunk when the left-hander recorded a two-over par 73 on the opening day.

But he bounced back in emphatic style on Friday with birdies at four of the first six holes.

Mickelson also added another birdie on the par-five 16th to finish with a bogey-free 66 - a score that was equalled only by his compatriot and tournament leader Skip Kendall.

Mickelson, who is four shots behind Kendall at the halfway stage of the competition, was understandably delighted with how things went on Friday.

"Well it was a wonderful round - I was very pleased the way I got off to a quick start," he said.

"You have to make birdies on the first nine holes here and I made it on four of them.

"I fought hard on the back and made some really good pars with some really good putts and I'm very pleased to get myself back in the tournament."

However, Mickelson, who played in 46 majors before he won at Augusta, is keeping his feet firmly on the ground.

"I still have a lot of work to do trailing by four strokes going into the weekend, but it's a lot better position than I was in after last night," he said.

"I thought a good solid round and I would get back in contention.

"Three or four under par would be a round that wouldn't be overly difficult but to shoot five or six I'd have to do something a little extraordinary."

The 34-year-old Californian is now hoping for a repeat performance on Saturday, but he knows it won't be easy.

"I may have to play another great round and if I'm going to make up shots I've got to do it on the front nine," he admitted.

"I've got to gain shots there and hang on to them on the back and my mindset tomorrow is to come out a couple of hours early and spend some time on the practice green like I did today.

"I spent an hour and a half and I made a lot of great putts - it really got the round going and hopefully I'll do the same tomorrow."