Southampton - Phil Mickelson, needing only a US Open title to become the sixth man to complete the career Grand Slam, will still be gunning for the elusive victory this weekend. 

Mickelson will celebrate his 48th birthday on Saturday playing in the third round after grinding out a second-round 69 to make the cut with two strokes to spare on six-over 146. 

"I played a lot better," said Mickelson, who was on the ropes after a first-round 77. "We got lucky with the conditions getting much easier. Our wave of tee times was significantly easier, and it shows how impressive Dustin Johnson is playing because he played in much more difficult conditions and he's beating everybody by a lot." 

World number one Johnson was the only man under par through 36 holes, leading the tournament with a four-under total of 136. 

Although he's 10 adrift - on a Shinnecock Hills course that has punished some of the world's best - Mickelson wasn't downhearted. 

He cited the 1995 US Open, also at Shinnecock, recalling that Neil Lancaster went out in benign morning conditions and shot an opening nine-hole score of 29 to thrust himself into contention. 

Mickelson, who will have an early tee time, thinks a similar charge isn't out of the realm of possibility. 

"If I can shoot that or anybody who just made the cut, I think there's potential," he said. "You just never know in this tournament." 

Despite his disappointing score on Thursday, Mickelson isn't disappointed in his game. 

Not known for consistency off the tee, he has missed just two fairways so far - at the third hole in both rounds, and has yet to make a double bogey or worse. 

"I drove it great. I didn't putt well, didn't chip well. I'm having trouble getting the ball close around the greens. I'm having trouble getting the ball to the hole is what I'm having trouble doing. I can't get it to release up the hill. 

"And then once it gets to the pin, it goes away, so I don't want to go past, and I'm just leaving everything short. Same thing putting. 

"So I'm going to have to be a little more aggressive around the greens, trying to get the ball to the hole. 

"I'm not thinking birdie," Mickelson added, "but I'll have to make some more."