American swimmer Caeleb Dressel impressed the swimming world, including Michael Phelps, during the world championships this year, where he took home eight medals, six of which were golds.

As far as Dressel's chances at winning eight gold medals at the 2020 Summer Olympics in Tokyo, Michael Phelps says his former teammate would need to be "perfect."

The 22-year-old is following in the footsteps of Phelps, and tied his record of three golds in one night for the second time at this year's worlds in Gwangju (the first time came in Hungary in 2017).

During a phone interview with The Associated Press, Phelps noted that Dressel would need to be perfect to win seven or eight gold medals in the 2020 Olympics.

"If there's someone who doesn't care how hard it's going to be, how hard they're going to have to work, how much pain they're willing to put their body through, we might see it," Phelps said.

The 28-time Olympic medalist also said that Dressel would be a "great addition" to the 4x200 free relay. 

"Clearly, he's got the speed. At this point, he's just got to have better endurance," Phelps said.

Just like his former teammate, Dressel can be his own worst critic, dissecting his races and looking for improvements during each one. 

"I always look for the bad," the Floridian said. "There's plenty to improve on. I know what to look for heading into next year, even for small meets. I take each event, and I have to learn from it."

After winning golds in the 50 and 100 free, 50 and 100 butterfly, mixed 4x100 free relay and 4x100 free relay, a silver in the mixed 4x100 medley relay and breaking Phelps' world record in the 100 fly, Dressel has the confidence to go into the 2020 Olympics.

"Two years ago I was a little scared, I'll admit, coming that close," Dressel said on nearly beating Phelps' 100-meter fly record in Hungary. "It can be a scary thought to do something that's never been done before."

This year the swimming star did not look scared at all and broke the previous record of 49.82 seconds with a time of 49.50, and did it with Phelps watching him from home. 

"I hope he was happy watching me," Dressel said. 

Phelps congratulated Dressel in a series of Instagram posts, and Dressel responded saying, "I appreciate you and what you've done for us."

While Dressel can be a harsh critic of his races, he said it was surreal to become a world record holder. 

"It's really special for me just to have that one little moment where I claimed I was the best in the history of swimming," he said. "Just a young kid from a small town, it's just crazy how far the sport can go."