Just watched the final shift from last nights game. Face-off was at 2:33 and Babock had Tavares-Kerfoot-Marner-Rielly-Barrie out. Washington won the draw and kept the puck in Toronto's end for about 30 seconds. About 30 seconds into the shift the Leafs finally came up the ice with possession and pulled their goalie. At this point, Hutchinson came off for Kapanen and Marner came off for Nylander. Kerfoot, Tavares, Rielly, and Barrie all stayed on. This is where I would argue the Leafs could have rather easily put Matthews on the ice. Either as the sub for Hutch instead of Kapanen, or by pulling Kerfoot off (he had just skated around the defensive end for 30 seconds) as the Leafs came up the ice (he literally skated right by the bench).
They were going for it. They pulled the goalie. They had Tavares/Rielly/Barrie out there and those 3 were likely playing as long as they could. I don't really see the reason to conserve Matthews at that point.