Somewhat remarkably, the Toronto Maple Leafs will improve next season if they can get goaltending on par with the league-average.
Across the past seven seasons, the league-average save percentage has been dropping to the point where it was 0.907 last season (per Hockey Reference). The Toronto Maple Leafs will be hoping to get better goaltending than that.
Petr Mrazek last season managed just a 0.888 save percentage; certainly below-par, hence his departure from the team this summer.
Jack Campbell was by contrast just above average with a 0.914 save percentage, but those numbers are really not the full story; his numbers were elevated by a Vezina-worthy November save percentage of 0.