Credit: Paul Gilham/Getty

Guess retirement didn't suit Michael Phelps. The decorated Olympics swimmer, who holds a record 22 medals, is coming out of retirement and is expected to compete at the Arena Grand Prix in Mesa, Ariz. -- his first competition since the 2012 games in London.

"As of today, I definitely expect him to swim," Phelps' coach Bob Bowman told USA Today.

Phelps, 28, has already entered to swim in the 100-meter butterfly and 100-meter freestyle events. "We're looking forward to it. I think it'll be great for the sport to have Michael compete again. We really don't have any expectations for what might happen," Bowman says.

The decorated athlete, who has already competed in four Olympic games, submitted for drug testing earlier this year and regained his eligibility to compete last month. No word yet on whether Mesa means Phelps will compete at the 2016 Games in Rio de Janeiro, Brazil.

"We just want to have some fun with it and see how it goes," Bowman cautioned.

Back in May 2012, pre-London, Phelps vowed he would go to Rio as a spectator only. "Once I retire, I'm retiring. I'm done," he said during a 60 Minutes interview.