The most popular knock on Joe Thornton: Jumbo Joe has never won a Stanley Cup in his 17-year career. Then again, the Toronto Maple Leafs have not hoisted hockey’s Holy Grail since 1967 — 12 years before Thornton was born. While he turns 35 on July 2, there still is gas left in Thornton’s tank, as evidenced by his 65 assists during the 2013-14 regular season, just three behind NHL leader Sidney Crosby. It should come as no surprise, then, that the Leafs are among at least six NHL teams who have kicked tires concerning Thornton’s availability. And why wouldn’t they? With centre being a position of need for the Leafs ever since Mats Sundin left, why not make an inquiry if someone of Thornton’s ilk might possibly come on the market? Leafs general manager Dave Nonis has often said that GMs often ask each other about the chances of pl​ayers being on the block. As he has pointed out in the past, it’s part of a GM’s job to do his due diligence. That doesn’t mean that it has gotten anywhere near the point of offers being exchanged. So, those of you who already have a Thornton deal worked out in which Dion Phaneuf goes to San Jose to replace the recently traded Dan Boyle, slow down.