No greater sign of Michael Phelps' progress in the pool was more evident than his performance this weekend at a U.S. Grand Prix Series meet in Santa Clara, Calif.

Michael Phelps' comeback prevents Ryan Lochte from retiring

Reuters.com reported that Phelps tired at the end of a 200-meter freestyle race on Saturday, finishing second to Olympic champion Yannick Agnel by more than a second after trailing by just 0.04 seconds at the race's midpoint.

"I got left like I was standing still in the last 50 by this guy," Phelps, standing next to Agnel, told Universal Sports, describing it as his "slowest 50 ever."

The race comes a day after Phelps competed in multiple finals for the first time since coming out of retirement. The Baltimore Sun reported that Phillips' races Friday in the 100-meter butterfly and the 100 freestyle represented the first time in nearly two years that he raced in more than one finals event.

Michael Phelps' comeback requires competition

That could account for his struggle Saturday to finish the 200 freestyle.

Phelps tied for first in the 100 butterfly with Tom Shields in a time of 52.11 seconds and finished second to Nathan Adrian in the 100 freestyle, clocking a time of 48.8 seconds.

Ironically, Phelps was happier with his 100 freeestyle performance.

"It's the third time we've done it (the butterfly) this year. We'd like to make a bigger breakthrough.

"I wanted to go under 49 and I wanted to go under 52. ... I got half of that."

The 28-year-old Phelps has been engaged in altitude training, Reuters reported, and is using the meet to prepare for the U.S. nationals in August and the Pan Pacific Championships in Australia later in August.

He is scheduled to swim in the 200 individual medley today.

Phelps told the San Jose Mercury News that he was 25 pounds overweight when he started his comeback, but looked to be close to his previous form at the Grand Prix.

Do you think Phelps can return to his gold medal form in time for the 2016 Summer Olympics? Comment below or tell us @SportsWN.