Matthews has been with the Leafs since the 2016-17 season and has been on some bad teams, so for him to call this the worst game since he entered the league means that it was pretty bad. It was the first time in the Sheldon Keefe and Matthews era that they have given up 9 goals, with the last time being in 2014 against the Nashville Predators.
The Leafs won't have much time to stew in their misery about their poor effort last night, which is probably a good thing, as they take on the Columbus Blue Jackets Saturday before heading into their Christmas break. It'll be interesting to see how they respond, but I would expect them, and particularly Matthews, to play one of their best games of the season.