By his own lofty standards, the former world number one has not played particularly well this year but a superb four-under-par 66 on Sunday in tricky scoring conditions confirmed the hard work he has put into his game in recent months is paying off.
"I was very pleased at Firestone, especially with my short game," Kaymer told Reuters.
"It paid off in the final round especially. I had one bunker shot that I holed and one chip-in and that really kept my round going. And it was nice to finish off with a birdie as well."
Kaymer tied for ninth at Firestone, where he recovered from a poor opening round of four-over 74 with scores of 67, 69 and 66.
"It was a great fightback," said the German, a 10-times winner on the European Tour who felt that many of the requirements on the heavily tree-lined Firestone layout had given him an ideal build-up to leafy Oak Hill.
"You had to hit a lot of fairways at Firestone. There were a lot of tee shots where you just have to stand on the tee box and 100 percent commit to it. I really enjoy those types of golf courses and this week is very similar."
Kaymer enjoyed golden seasons in 2010 and 2011, the highlights being his first Major win at the PGA Championship, in 2010, his rise to the top of the world rankings and a maiden crown in one of the elite World Golf Championships (WGC) events.
Though he shone for Europe at last year's Ryder Cup when he secured the vital point to retain the trophy, beating Steve Stricker in singles, his overall form dipped in 2012 and this season has been a mixed bag.
"Very average, I would think," Kaymer, 28, said of a winless 2013 campaign that includes three top-10s in 13 starts on the US Tour and a best finish of a tie for fifth at the Byron Nelson Championship in May.
"But I have worked a lot on certain things, on my short game and my swing, and I am certainly aiming for much more success over the next year, year-and-a-half than this season.
"My form has been a bit like a big puzzle that has to find its own way to get together, but it's getting there."
Tiger Woods has been installed as a heavy favourite for the PGA Championship after coasting to a seven-shot victory at Firestone, but Kaymer rejects the notion of a one-horse event.
"To be honest, I don't really care," he said. "I try to do my own game.
"Obviously Tiger seems very confident at the moment and if you have won an event eight times, like he has at Firestone, you know exactly where to hit it and the experience you have gives you a lot of confidence.
"But for me, this week is all about playing as good as I possibly can. There are many other good players out here too."
Kaymer has been grouped with defending champion Rory McIlroy of Northern Ireland and 2004 winner Vijay Singh of Fiji for the first two rounds at Oak Hill.
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