Henrik Stenson felt he never reached his best form after falling away during the final round of the US PGA Championship.
The Swedish Open Championship winner carded a one-over 71 in the final round at Baltusrol on Sunday to be tied for seventh.
Stenson had looked likely to contend, but a double-bogey at the 15th saw him slip away and end up six shots behind champion Jimmy Walker.
The 40-year-old said his game never reached a level he wanted on the final day of the year's last major.
"It was a long day. I never felt like I brought my A game. I was struggling most of the day," Stenson said.
"I think I hit more poor shots in the two rounds today than in the previous six or several rounds combined.
"I didn't bring my game and I didn't make a putt all day, I felt like.
"Despite that, I thought I was hanging good. I was trying to push, which I had to. I was two or three behind coming into the last five or six holes.
"I just winged it over a lot, which was funny enough, probably the best shot of the day, little three-quarter nine-iron, I just overcooked it [on 15] and went long and I made double and that was the end of it for me."
Walker claimed his first major title with a one-shot win, holding off world number one Jason Day.
Daniel Summerhays ended up third, and the American was still struggling to believe his best major performance at his news conference.
"Well, what a thrill. I'm still shaking a little bit. That was pretty amazing on the 18th hole. I had an eagle look," he said.
"I know I was a little bit behind. Just to have a chance to maybe win a major championship was a thrill of a lifetime.
"Six birdies on the last 10 holes, couldn't ask for a better finish. I'm going to sleep really well tonight after 34 holes of golf out there."