Irvine, United States: Olympic great Michael Phelps settled for silver in the 100-metres butterfly at the US Swimming Championships on Friday, falling by one one-hundredth of a second to Tom Shields.

Hours after throwing down the fastest time in the world this year of 51.17sec in qualifying, Phelps let the tension of the final — and the pressure of trying to qualify for the Pan Pacific Championships — get to him.

He mistimed his turn, just a little, and it cost him on the closing leg when his trademark late surge wasn’t enough to carry him past Shields, who won in 51.29sec to Phelps’s 51.30. Tim Phillips was third in 51.54.

“I knew once I hit my 16th stroke and I was still a little long going into that wall, I knew it just killed all my momentum,” said Phelps, who is swimming in just his fourth meet since coming out of a near two-year retirement in April.

“I need more training, I need more endurance, I need more comfort with my stroke,” he added.

Coach Bob Bowman said he thought Phelps looked uptight before the race — something that was never an issue when Phelps was the dominant swimmer in the world, putting together a career that included 22 Olympic medals, 18 of them gold.

“It’s not fitness, it’s the knowledge that he’s getting up here against these guys that are on fire and he knows what he’s done to get here, and it ain’t what he used to do to get here,” Bowman said.

As the second-place finisher, Phelps will likely still qualify for the US team for the Pan Pacific Championships in Australia August 21-25.