"The Celtics are very happy with how hard Jayson Tatum has been working at his rehab, and his level of focus and intensity in the rehab process," Bertrand said.
"(Tatum) did not leave town. He has been here the entire time. … Since the injury, he has not left town and he has been inside the building at the Celtics’ facility with their people and their team almost every single day for months."
It's not uncommon for injured players to be away from the facility during their rehab, especially during the offseason. For example, there were reports before Damian Lillard re-signed with the Portland Trail Blazers that he planned to rehab from his torn Achilles in Portland, regardless of where he signed.
But Tatum apparently has been doing his entire rehab in Boston under the guise of the Celtics' training staff at their facility. And his commitment to that rehab is such that he's been in the building virtually every weekday, per Zolak.
"He’s taken trips. He’ll go away to a certain island or something," Zolak said. "But he’ll get his Friday workout in, fly down, work out there at that place, fly back late Sunday night, and be right back in the building on Monday morning."
"All summer long, all he did was take weekend trips away," Bertrand added. "He did not go away for any extended period of time, because he wanted to be back to work on his rehab.
"He’s doing things that nobody asked him to do."
https://www.nbcsportsboston.com/nba/boston-celtics/jayson-tatum-injury-rehab-process-mazzulla/732454/?amp=1