My initial estimate when they said 2-4 weeks was March 14th, based on the schedule.
The Leafs schedule thankfully (in terms of the Matthews injury) went very light almost right after Papi got hurt, and it doesn't pick up until March 14th. That's when it goes back to 3-4 games per week, as opposed to this weird week-and-a-half or so when its been much lighter.
So even if Matthews seems like he's ok for Saturday, its easy to see management electing to rest him and tack on another four days off, just in case. Makes sense based on the Leafs likely not moving out of 3rd place in the Atlantic, and could be a huge blessing in disguise come playoff time.
Time will tell.