No, that was not his role. That is just getting massively outplayed. If you think his job was to get massively outplayed in every way, and that was the best they could possibly hope for, then you're really just arguing how amazing and massively valuable and impactful Matthews is.
I'm pretty sure it was reported that Matthews hit more posts than any other player in the 1st round of that year's playoffs.
If I remember correctly, Danault did have better moments in the playoffs after getting crushed by us, but the 1st, 2nd, and 3rd reason they made their run was Price.
Columbus continued getting hot goaltending into the Tampa series. Through the same amount of ice time, the SV% was almost identical. Korpisalo set the all-time playoff save record in that series. 0.950 goaltending is obviously not sustainable. Eventually, it runs out and often rebounds the other direction. Columbus actually still ended with a better series goal differential than any other team Tampa faced on their way to the cup.
Yup, Danault during the regular season:
xGF%: 57.17
Goal differential: 59.76
xGA/60: 1.86
Dominant two way player (with a stronger defensive bent) on one of the best lines in hockey:
Danault against the Leafs:
xGF%: 34.80
Goal differential: 0.00 (0 goals for, 3 against and lucky to have it that low)
xGA/60: 3.23
The worst playoff series of his career and actually led to that league-leading line being broken up after a game 5 victory. The coach had to do something as they were getting eaten alive by the Matthews line and his big problem was breaking that line up and with no Tatar, they could never get their offensive mojo going again. Matthews with 11 takeaways and 1 giveaway 5v5.....Danault with 2 takeaways and 7 giveaways.....
Danault the rest of the playoffs:
xGF%: 48.17
Goal differential: 55.19
xGA/60: 2.13
Again, with no Tatar on the line anymore hurt the line offensively a bit but they returned to solidish numbers not having to play Matthews, especially defensively. Ducharme should have recognized this and reunited the line instead of blaming Tatar for Matthews' dominance. It might have led them to a cup. Ducharme really is one of the worst coaches to make it to a finals IMO.
Goals allowed against the Leafs by the Danault line: 3 (and they got lucky)
Goals allowed the entire rest of the playoffs by the Danault line: 3
On the flip side, just look at the Matthews/Marner lines numbers the last 3 seasons:
Regular season:
xGF%: 62.70
Goal differential: 63.48
Playoffs:
xGF%: 64.70
Goal differential: 63.71
Some really stable numbers there. The rest of the team, not so great. The PP has been a real disaster too.
As a line though, Matthews/Marner have been one of the best in the league, playoffs or not.