Jennings, a 25-year-old right-hander, needs one victory to tie Kevin Ritz for second on the franchise list with 39.
The NL Rookie of the Year in 2002 when he won 16 games, Jennings has posted a 38-29 record in four seasons.
He has won four of his last six decisions despite a 5-3 loss at Cleveland on Sunday, during which he gave up five runs and 10 hits over 7 1-3 innings. Jennings hadn’t gone more than six innings in any of his four previous starts.
“To go out there and, even though we lost, get into the eighth inning is somewhat satisfying,” Jennings said. “It’s something positive to take away.”
The Rockies ended a five-game losing streak with a 9-8, 10-inning victory in the series opener on Friday.
Charles Johnson hit a three-run homer with two outs in the ninth to tie the game, and the Rockies scored twice in the 10th on bunt singles.
The Tigers have lost two straight following a season-high six-game win streak.
“I told them not to be fooled by their record,” Tigers manager Alan Trammell said referring to the Rockies sitting 20 games below .500. “Besides, I’ve been here enough to know the strangest things happen in this ballpark that they need to stay in the game.”