I didn't follow the thrashers much last year but with the game being out of reach at 6-1 around the middle of the second and Noel leaving pavelec in, he's not going to put Mason in. With the 7th goal then he knew to get pav's out. Some goalies like to try and battle it out especially for Pavelec who had a night off last night.
You don't let your #1 who is still growing and gaining confidence in after 5+ goals imo regardless of the situation.
It's nothing to do with him fighting out of it or battling through, it's avoiding embarrassment and regression. I can already count a few times earlier this year he was left in net when he should've been pulled for his own sake and tonight was no different.