Michael Phelps could win two or three individual gold medals at the 2016 Rio Olympics and again return home as America's top swimmer, former U.S. swimming great John Naber believes.

Already the most decorated Olympian of all-time with 18 gold medals, Phelps' return to competition after a two-year retirement was greeted with apprehension and skepticism but the tide has quickly turned.

While no one expects Phelps to come close to his eight gold medal haul at the 2008 Beijing Games or the six he swept four years earlier in Athens, Naber believes he could match or even better his haul from London where he stood atop the podium four times.

"He'll come home, if not America's most decorated swimmer, one of the top three," an assured Naber told Reuters during a break in United States Olympic Committee General Assemblymeetings on Thursday. "I think he can win individual gold medals, I think he can win two or three individual races and a couple of relays

"I expect he will win four or five medals, the fact that he swims for the United States if he makes those relays teams those medals are going to be coming," said Naber, a five-time Olympic medalist, including four gold from the 1976 Montreal Games.

Since Phelps first tested the comeback waters at a low key meet in Phoenix in April progress has been steady rather than his usual spectacular.

He has had to deal with the unfamiliar sting of losing and re-calibrating his own sky-high standards.

But the results and times have slowly improved through the U.S. nationals and his international return to competition at the Pan Pacific championships in Australia in August where he finished with gold medals in the 100 butterfly, 4x200 and medley relays as well as silvers in the 200 individual medley and the 4x100 relay.

The 100m butterfly is one of two individual events that Phelps won at three successive Olympics.

If he qualifies for the event at Rio, he will automatically make the U.S. men's medley relay team, which has never been beaten at the Olympics.

HELPING SPORT

"He doesn't need any more gold medals to establish his reputation. I don't think he's going to hurt his reputation by not winning eight more gold medals," said Naber. "He is doing it the right way. He is being very gracious when he loses and appropriate when he wins.

"There are handicaps Michael has to deal with but by his presence he is bringing attention, sponsors, ticket sales. He is helping the sport at his own personal expense to the benefit of all other athletes who are competing there"

While Phelps and longtime coach Bob Bowman have remained tight-lipped about their exact plans, there is little doubt the 29-year-old swimmer is targeting an attack on the top of the podium inBrazil.

But much work needs to be done before Phelps can once again eye the Olympic summit.

Ahead lies next year's world championships, which will provide a more precise barometer of Phelps' potential, followed by the U.S. Olympic trials as he attempts to avoid the disappoint that has sank so many other comebacks.

American Mark Spitz, Russian Alex Popov and more recently Australian Ian Thorpe have all failed miserably in comeback bids.

But with the help of Bowman, Phelps has clearly mapped out his return, finding the right combination of motivation and commitment to see him through the long grueling hours in the pool that caused so many others to abandon their attempts.

"What I do remember is that as long as my world record stood I could say to myself, "If I was in that pool I would still be winning"," said Naber, whose world records in the 100 and 200m backstroke both stood for seven years. "The moment my world record fell all desire to race and lose went away.

"Frankly after I retired I never wanted to go back to that regiment again. For me it was a very easy realization. It wasn't painless but it was easy to say I belong on land now."

When Michael did a short retirement nothing he saw or participated in filled his batteries the way that swimming does, Naber said.

"He has mentioned that he is enjoying it more now that I guess because he no longer has to go for the 22 medals, he can just relax and enjoy it more. It is familiar, it's comfortable it pleases him.

"I play Sudoku for the same reasons."