Michael Phelps has already come out of retirement once, so despite saying that his triumphant showing in the Rio de Janeiro Games allowed him to "close the door" on swimming, would it be any surprise to see him competing in the 2020 Games?

Probably not. But as of now, Phelps is official retired after filing paperwork that removes his name from the U.S. drug-testing program. That makes the 31-year-old ineligible for any high-level competition and typically serves as the official end to an athlete's career.

Phelps told Nick Zaccardi of NBC Sports on Monday that what sealed his decision to finally hang up his goggles was something to which even we mere mortals can relate: He was sick of all the paperwork. Athletes at his level must constantly file updates on their movements, so that drug-testers know where to find them at a moment's notice.

Calling that relentless system of alerting officials to his whereabouts "brutal," Phelps said that he told his agent, "Get the papers, can we just sign these things, so I don't have to do the daily updates and everything?" He added, "I'm still in the pool [recreationally]. I'm still not coming back."

That agent, Peter Carlisle, is also a close friend of Phelps who presided over the June wedding that the latter kept a secret through August's Olympics in Rio and into October. The 23-time gold medalist told Zaccardi that he and his then-fiancee, Nicole Johnson, hastily held a "backyard wedding" to make it easier for her and their infant son, Boomer, to travel together under the same last name.

In Rio, Johnson and Boomer, plus Phelps's mother Debbie, were able to cheer him on as he won five gold medals and a silver, giving him a total of 28 total medals and adding to the record he already held. Shortly before serving as the flag-bearer for the U.S. team, Phelps had said, "To have our firstborn be able to watch - I'll say this just, in case I come back - my potential last Olympics. Just so you guys don't beat me to death if I come back, I'm just going to say that: To have him watch the potential last races of my career is something I look forward to being able to share with him."

Of course, Phelps said similar things following the 2012 London Games, after which he also filed paperwork to remove his name from the drug-testing pool and "officially" retire, then unretired by adding his name back into the program in 2013 ahead of his comeback. Perhaps this time will stick, and his Rio races will be, in fact, the final ones of Phelps's incomparable career.

"Yes, I am done. I said it four years ago, but I actually am really done," Phelps said with a smile Monday at the Golden Goggles in New York, where he accepted an award for the Male Race of the Year for his victory in the 200 butterfly in Rio (remember the "Phelps Face"?). Now a husband and a father, he looked like someone very happy to end his swimming career on the highest of notes.