So does Toronto GM Kyle Dubas, who said he sees Thornton helping on the power play and in the locker room.
In 2017, when Dubas was an assistant to then-GM Lou Lamoriello, the Maple Leafs made a significant push to sign Thornton, who was a free agent but re-signed with the Sharks.
"I gave it a long, hard thought," Thornton said. "And it just didn't work out back then. And now I honestly just felt like it was a great move for the family. It's going to be an easy transition for my kids, for my wife.
"It just honestly felt like the right time to make the move and I'm just super excited."
Dubas' admiration for Thornton dates to growing up in Sault Ste. Marie, Ontario, when he and his minor hockey league teammates would go watch the gangly teenager play for the Greyhounds of the Ontario Hockey League from 1995-97. Dubas became a stick boy with the team the following season.
Asked if he remembered Dubas from his junior hockey days, Thornton laughed.
"To be honest, I can't remember what happened two weeks ago," Thornton said.
Dubas can.
"He was just a dominant player. And even as a 16-year-old, as dominant as he was skill-wise and with his size, he was also one of the tougher players that had come into the program," Dubas said. "And I think the combination of all those things, certainly in Sault Ste. Marie, makes you revered forever.
"Obviously, he's gone on to be one of the most revered players in the history of the franchise."
Much the same way he was in San Jose.
But now it's time to work on a new legacy in Toronto. With Dubas, coach Sheldon Keefe and several players reaching out the past week, Thornton said he already feels welcome. Forward Jason Spezza contacted Thornton after the signing and offered to give up his No. 19, Thornton's longtime number, to the newcomer.
"Nice gesture, but no way. That's his," said Thornton, who'll wear No. 97.
By coming to the Maple Leafs, Thornton returns to his southern Ontario roots. He was born in London, Ontario, and grew up in St. Thomas, 125 miles southwest of Toronto. His parents, Wayne and Mary, still live in the community, where the local arena is called the Joe Thornton Community Center and where Joe owns a farm about eight miles outside of town.
"Obviously my parents are [near] so that was part of [the decision]. They can be around the grandkids a lot," he said.
In the end, however, the deciding factor was the talent on the Maple Leafs roster.
"It was a little bit family but mostly hockey," Thornton said.
And a chance to finish his career with a Stanley Cup championship.