Rory McIlroy reflected on a day of missed opportunities after settling for a second consecutive 71 at the 97th PGA Championship, while Jordan Spieth went four shots better at the halfway stage.
The defending champion was determined to take advantage of the benign early conditions at Whistling Straits and make strides up the leaderboard, but he managed only pars at his first six holes before finally getting a birdie putt to drop at the 16th.
McIlroy was then furious with himself for scrapping his way to a double-bogey six at the 18th, but he got both shots back with one shot at the long second as he chipped in for a galvanising eagle.
He holed from eight feet for birdie at the sixth, but he bogeyed the next after pulling his tee shot in greenside rough before McIlroy parred in to remain two under for the tournament.
On a day when Japan's Hiroshi Iwata equalled the lowest score in major history with a 63 and playing partner Jordan Spieth shot 67, McIlroy admitted his short-game was not up to scratch following his seven-week lay-off with an ankle injury.
"I felt like tee to green I hit the ball pretty well, I'm probably just not as sharp with the short game as I would like to be," the world No 1 said. "It was good to get the two shots back that I dropped on 18 and I gave myself good chances on the third and fifth, but did not take them.
"There's plenty of chances out there and if I can convert a few hopefully there is a low score in me.
"I felt like I played better than what the score reflected, so I'm a little bit annoyed. I felt like I should have got that ball up and down on seven and then I had a great chance on eight for birdie and didn't take that. A couple of days in a row where I haven't finished the round of golf the way I wanted to.
"I don't know if it's rust or I just didn't putt well, so maybe just work on that a little bit before I tee off tomorrow and it would be great to hole a few more putts, because I feel like I'm giving myself plenty of chances.
"Probably one of the most surprising things about yesterday is how quickly I got back into the mindset of tournament golf and being aggressive. That hasn't really been an issue, it's just being a bit more efficient, whenever you give yourself chances, take them, and be able to get it up and down when you put yourself out of position."
McIlroy now has his work cut out to hang onto his world No 1 ranking ahead of Spieth, who enjoyed a run of four birdies in six holes mid-round as he moved smoothly to six under for the tournament.
The highlight of Spieth's round was a superb bunker escape that found the hole for an unlikely birdie at the 18th, and he was delighted with another good day's work in his bid to become only the third player in history to win three majors in a year.
"We are freerolling now," Spieth joked after making the cut in the tournament for the first time at the third attempt. "I'm just happy to be back in contention and position. If I'd had a bit of a lull today it would have been too hard to make up.
"With a couple of chip-ins for the week and really smart course management and good speed control, we have been able to hold ourselves in there. But in order to keep shooting the rounds like today, I'm going to need to drive the ball a little bit better and make a few more putts, which are really the two keys for me this weekend, because it's just going to get more challenging with pin locations and firmness of greens."
On his holed bunker shot for birdie at 18, Spieth's 16th chip-in of the season, he added: "It's arguably the best of the year given the position it was in. It was a great spark to get things going, get a little confidence, a little pep in my step.
"I feel good. I've got a chance to win a major championship. Just thinking about that gets you enough adrenaline that there won't be any issues. I noticed last year for the first time I felt fatigue and felt like I had overworked and kind of burned out the end of the year, as we had to go through the four play-off events without a break and then into the Ryder Cup.
"This year I've done a better job of when I take time off, when you limit the practice coming back, how to prepare. As far as mentally in this position, the way the year's gone, I approach each event as if it's the only event of the year when I stand on the first tee. That gets me through it.
"I'm sure at the end of this year, it will be nice to sit back and hang the clubs up for a couple weeks, but until then we have got a lot to play for."
