8 game sample doesn’t mean much. Leafs goaltending has been awful the majority of the year, outside of the start of the year where Matthews missed some of those games and then started slow. During his 51 in 50 period, the Leafs had a .892 SV% and were giving up 3.37 G/GP. They needed all the offense they could get. The team is also 5-8-2 in the games Matthews doesn’t record a point.
I think the Leafs would suffer pretty similarly this year in terms of falling down the standings without Matthews as Calgary would without Gaudreau or the Oilers would without McDavid. They might be less likely to fall out of the playoffs, but that’s because there’s a huge cushion in the East, which shouldn’t really be held against anyone.