Lyons, a lefty, has appeared in 23 games, including 12 starts, in 2013 and '14 for the Cardinals. He has a 2-8 career record with a 4.62 ERA.
"We have a pretty good idea of what he can do, just the consistency of holding through a game," Cardinals manager Mike Matheny said. "Holding it from start to start, and part of that is just a young player, and hopefully he's making those moves in a right direction."
Right-handed reliever Carlos Villanueva appeared to be a frontrunner for the start after pitching 3 2/3 innings of scoreless relief for Cooney on Thursday. But the Cardinals were forced to use him during Saturday's extra-inning win over the Pirates.
"We had Tyler in our mind here for awhile," Matheny said. "If we hadn't used Carlos and he was completely fresh, we would have probably brought Tyler along and weighed our options at that point and one of them start and one of them piggy back, and we had that kind of going for us. But Tyler was mostly likely going to be the guy, but whether or not he got the start depended on how we used Carlos and the rest of our 'pen."
Joe Harris is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.