The Rio Olympic gold medallist went under the knife in Sydney this week with doctors removing a troublesome bursa.

Chalmers was due to race this weekend but facing ongoing shoulder soreness he and coach Peter Bishop visited the specialist who had operated on swimming great Ian Thorpe.

"When Kyle came back after COVID he was still sore and we decided we had time on our side so let's get it looked at," Bishop told Swimming World magazine.

"He had already had some cortisone injections and then the PRP (Platelet-rich plasma) therapy which was a slow progression.

"But then when the borders opened between South Australia and NSW and so we could actually fly to Sydney to get the opinion of a specialist recommended by Swimming Australia and actually Ian Thorpe, who was also seeing the same surgeon."

Chalmers had the operation on Tuesday where the bursa was removed as well as a "general clean-up".

"From initial reports the doctor is very happy with the rest of the structures in the shoulder so there are good signs and my understanding is that rehab will take weeks and not months ... and we should be good to go," Bishop said.

Chalmers, 22, posted a photo on his Instagram account, saying: "Rehab starts now, bring on Tokyo 202One".

Australian Associated Press