San Jose Sharks captain Joe Thornton isn't really on the market, but if he were, the Toronto Maple Leafs would be among "at least six NHL teams" that would have significant interest according to a report by QMI's Mike Zeisberger.
Zeisberger specifically suggests that the Leafs and "at least" five other teams have already 'kicked the tires concerning Thornton's availability.' A first-line center and premiere playmaker would make a lot sense for a lot of teams, so that level of potential interest shouldn't come as much of a surprise.
Ever since the Sharks bowed out of the postseason following four straight losses to the Los Angeles Kings in the opening round of the Stanley Cup playoffs, there have been significant rumblings about the potential for change in San Jose. TSN's Bob McKenzie even suggested in May that Thornton could be on his way out of Northern California this summer.
The key here isn't the "interest" that teams like the Maple Leafs have in a player of Thornton's caliber. The key is whether or not the Sharks decide to jettison a player that - even on a club with talented younger pieces like Logan Couture and Joe Pavelski - still draws the most attention from opposing team's defenses on a nightly basis.
Anyway, for now it appears that Thornton isn't "on the market" per TSN's Pierre LeBrun:
Right now [Thornton being on the market is] not the case but the Sharks have made it known they're rebuilding. What does that mean for a veteran like Thornton – does he want to be on a rebuilding team? That remains to be seen.
Basically several teams including the Maple Leafs would be interested in a star player if he becomes available, but he's not available at the moment and surely won't be unless a team - like the Maple Leafs perhaps? - make a significant offer.
Just so long as the Sharks don't ask for one of the Maple Leafs untouchable players, like Tyler Bozak, in return.