Matthews (upper body) has been ruled out for Monday's game against the Jets, Ken Wiebe of The Winnipeg Free Press reports.
Matthews recently aggravated his upper-body injury, and he'll be unavailable for a second consecutive game ahead of the league's Christmas break. He'll have several days to rest during the layoff before the Maple Leafs face the Red Wings on Friday, while Connor Dewar will likely remain in the lineup Monday.