The only thing that's really eluded Matthews to this point in his career is, well, success in the postseason. Matthews has 44 points in 50 career playoff games but has only made it out of the first round once, in last year's playoffs.
He'll have plenty of time to exorcise those demons with this extension. This deal will keep Matthews with the Maple Leafs through the 2027-28 season, at which point he'll be 30-years-old.