Is Michael Phelps hinting at a comeback?

This week, Michael Phelps posted the above photo on his Instagram account with a not-so-subtle tagline: "One on one training session with @coach_bowman !!!"

"Coach Bowman," of course, is Bob Bowman, Phelps' coach through much of his career. Could this be a hint at a comeback for the Rio Olympics in 2016? Several sources, including Phelps' competitor/teammate Ryan Lochte, have indicated in recent months that they expect Phelps to return. Phelps himself has remained mum on the subject, but if he does decide to come back, Bowman would be the one to have on the deck.

Phelps has no driving reason to return; he's already the most decorated Olympian in history, with 22 medals total, 18 golds. And returning would mean a return to years of grinding practice. Does he have it in him? Only Phelps knows, and he ain't talking.

-Follow Jay Busbee on Twitter at @jaybusbee.-