Hayden Steele's fifth-inning hit forced an error by Joplin Outlaws' third baseman Matt Turner, allowing the go-ahead run to score in a 4-3 Mustangs win.
The victory plus a doubleheader sweep of Chillicothe by Omaha puts St. Joseph up 2 1/2 games in the division. With four of their last nine games coming against the Mudcats, the Mustangs control their own destiny to play for the MINK League Championship. The top teams in the North and South Divisions play for the league title in a best-of-three series.
After being shut out in their last trip to Joplin, the Mustangs stuck first when Joe Koerper grounded into a run-scoring fielder's choice in the first.
The Outlaws hung all three of their runs off newcomer Kevin Sweeney in the next frame. Sweeney still managed to pick up his first win for St. Joseph, allowing three runs on eight hits over seven innings while striking out six batters.
Mike Sherburne cut the deficit in half in the third, plating Koerper with a double to the left field wall. He then scored the tying run, taking advantage of a pickoff move against Kyle Richards by racing home from third.
St. Joseph returns to Phil Welch Stadium on Tuesday to face Clarinda.