Yeah. Matthews want Calvillo to be happy so he generally leaves it to him to get out of a game. And as AC can rack up a second 6000 yards season, I bet he'll stay in as long as possible. If the Als have a playoffs spot assured before the last regular season game, but AC is at 5750 yards before the game, look for him to start.
Sportsmen, to stick with your question, I think Matthews kept his starter in because he did not want to allow the Renegades to eat back some of the lead. Two reasons for that:
People keep on saying the Als can't keep on playing solid to the last whistle (which was true in many games this year). So if the Rens come back and score... say... 14 points in the last 4 minutes, that won't give them the W, but that will keep the question marks floating around the team. Matthews don't want that.
Matthews wants to establish he can still crush his opponents. That will assure his survival as a head coach. Squeakers like the 0:00:02 victory against the Esks in July are still worth two points in the standings, and we'll take them, but that's not what a coach needs to re-establish credibility when every one is questionning whether he still has it or not.
Not to mention, when the Als collapsed against Ottawa on July 1st, they blew a 23 points lead. So that number "23" was probably significant for Matthews. He wanted to show we can hang to that.
Of course, all this brilliant analysis is just my personnal beliefs. Maybe Matthews just forgot to call back Calvillo because he was picturing small black and white ducks playing guitar in his head.