MESA, Ariz. — Michael Phelps ended the first meet of his comeback on an odd note Friday, using his butterfly stroke to swim a 50-meter freestyle race that’s never been part of his repertoire.

He was swimming to tinker with his form, not to win.

And the race proved a side note to a week with greater implications for the record-setting Olympian and the sport he has loved since childhood.

Phelps’ return sent a charge through what would have been a routine meet, and the shock waves will continue to ripple through the swimming world as long as he’s around.

For the sport, Phelps is a signature star, capable of producing ticket sales, media attention and Olympic hype like no other.

For him, the comeback is both a source of joy and a potential marketing boon worth millions of additional dollars.

For swimming’s rising talents, Phelps is like a living myth, a previously abstract standard of excellence who might now actually jump in the pool with them.

For old rivals, he’s inspiration to get the competitive juices flowing for a few more years.