The Toronto Maple Leafs didn't lose in the playoffs this year because of Mitch Marner, despite what a million angry Leafs Fans will tell you.
The Toronto Maple Leafs lost because their GM made the horrendous decision not to trade for a goalie mid-season.
Instead of making the trade pretty much everyone knew he needed to make, Brad Treliving entered the playoffs will Ilya Samsonov, a goalie who went unclaimed on waivers less than three months before the playoffs.
It proved to be the Leafs undoing, as Samsonov was not good and lost the net to Joseph Woll. Unfortunately, Woll is incredibly injury prone and was predictably unable to go in game seven, so the net reverted back to Samsonov and the Leafs lost in overtime on a very savable shot.
In addition to needing a goalie, the Leafs also have the problem of Auston Matthew's Prime.
The Prime of the Best Player in Franchise History cannot be approached lightly. You don't get many kicks at this can. The Leafs know this, and that rules out any chance or the Leafs going with a Joseph Woll + Decent Back-Up tandem.
Woll might yet be an amazing starting goalie, but he's only played 39 career NHL games and seems to be constantly injured. Unfortunately, it is too risky to go with him and someone like Laurent Brossoit, no matter what the rumorus say.
The Leafs recent history and the age of their best player leaves them little choice but to pursue a star goalie.
The Leafs have tried many things over the Auston Matthews Era, but one thing they haven't done is put Matthews and Marner with a top goalie.
Therefore, expect the Toronto Maple Leafs to pursue an elite goalie this summer, likely in the next week. (much of this info from capfriendly.com).