Hayward broke his leg in the first quarter of the season opener and missed the rest of the 2017-18 season. The Celtics reached Game 7 of the Eastern Conference finals before losing to the Cleveland Cavaliers.
The team says his leg and ankle are sound, but the plate and screws that were implanted to help the injury heal were irritating Hayward's tendons. He is scheduled to resume basketball activities in six to eight weeks and be ready for training camp.
"Gordon felt like he was making great strides, getting close, but he still had a little bit of pain in one little spot. [It] persisted over the last couple months and they felt it was being caused by the hardware and they just took the hardware out," Celtics president of basketball operations Danny Ainge said in an interview with 98.5 The Sports Hub on Thursday.
"They just felt like they were going to get the hardware out and his bone had completely healed and the muscles and the tissue and everything is all healed. They just wanted to get that hardware out, so the safest bet is him being 100 percent by next year. There wouldn't be lingering effects," Ainge said.
Also on Wednesday, the Celtics said center Aron Baynes had successful surgery to repair a nasal fracture he sustained during Game 6 of the conference finals. He is expected to be back on the court in two to four weeks.
ESPN's Chris Forsberg and The Associated Press contributed to this report.