Boston Celtics star Jayson Tatum admitted he is still battling with the after-effects of coronavirus despite returning to NBA action three weeks ago.

Speaking ahead of Boston's 112-99 win over the Denver Nuggets on Tuesday, where Tatum contributed 21 points, six rebounds and eight assists, the All-Star revealed he was still experiencing respiratory issues during games.

Tatum tested positive for COVID-19 in early January, alongside some team-mates, forcing three Boston games to be postponed.

"I think it messes with your breathing a little bit," Tatum told reporters.

"I have experienced some games where, I don't want to say struggling to breathe, but you get fatigued a lot quicker than normal. Just running up and down the court a few times, it's easier to get out of breath or tired a lot faster; I've noticed that since I've had COVID.

"It's just something I'm working on. It's gotten better since the first game I played, but I still deal with it from time to time."

The Celtics have a 7-10 record since then, slipping to third in the Atlantic Division of the Eastern Conference, behind the Philadelphia 76ers and Brooklyn Nets.

After a period of quarantine, Tatum returned to the court with 24 points against the Chicago Bulls on January 25.

Tatum has not missed any of Boston's 12 matches since returning, top scoring for the Celtics on seven occasions, insisting the issues have not affected his performances or output.

"It's gotten better obviously from the first game I came back and played, but I guess it's just a long process," he said.

"I've talked to other guys that have had it and they say they experienced the same thing and it kind of just gets better over time. But as much as we play, I guess it takes a little bit longer.

"You've got to take it on the chin when things aren't going great and you're not playing how you should be."