Rory McIlroy claimed a one-shot lead at the halfway stage of the US PGA Championship, but a number of world-class contenders were hot on the world number one's heels at Valhalla.
Australian Jason Day carded a superb 65 and former US Open champion Jim Furyk a 68 to share second place on eight under par, with Finland's Mikko Ilonen and American pair Ryan Palmer and Rickie Fowler a shot further back.
And Phil Mickelson eagled the 18th in a round of 67 to lie just three shots off the lead on six under par alongside Austria's Bernd Wiesberger.
Day has suffered a number of illness and injury problems since winning the WGC-Accenture Match Play title in February and was forced to withdraw from the Bridgestone Invitational last week suffering from vertigo.
But the 26-year-old has already had several near misses in major championships and is determined to break his duck this weekend.
"I'm excited. You can't not be excited to be in or around the lead in a major championship. Obviously they are the hardest tournaments to win," Day said. "I'm looking forward to it. It's going to be a lot of fun.
"I've been close a lot of times. I've said it before, I just have to keep knocking on the door and hopefully it will fall my way one day. It's either hope it falls my way or just knock the door down and take it.
"I'm clearly not the favourite with how Rory is playing, especially over the last few tournaments. It's going to be tough to beat him, but then again there's a lot of great golfers behind us that are in form, as well."
Fowler has already finished fifth, second and second in the year's previous three majors and said: "I'd say each major I've felt more and more comfortable.
"The Masters is the most comfortable I had felt in a major and then being in the final group at the US Open and another final group with Rory at the Open, I felt more comfortable there than I did with Martin (Kaymer at Pinehurst).
"It doesn't feel like a big stage. I feel like I'm out there having fun. I like where my game is at. It will be a battle this weekend and I'm looking forward to it.
"Rory is obviously on top of his game right now. He's been driving the ball very well. When he does that, it kind of alleviates any stress from anywhere else and he's able to go full throttle and not really let up.
"The Open definitely wasn't the last final group of a major that him and I will be a part of. Maybe we'll get another one for Sunday."
Mickelson has recorded just one top-10 finish all season - in Abu Dhabi in January - but came into the week on the back of a closing 62 at Firestone on Sunday.
"I fought hard, I didn't get off to the greatest start but was patient with the round," the five-time major winner said. "It came to me a little bit there in the middle. To shoot four-under puts me in a good position for the weekend.
"Obviously Rory is playing great golf. There's a lot of guys at four, five, six, seven under par and out of that group somebody is going to get hot. I think that I have a hot round in me, too."