Omar Infante left Friday night's game against Detroit with a left oblique strain and is not expected to return by October, reports Kansas City Star beat writer Andy McCullough. MLB.com writer Jeffrey Flanagan reports Infante will return to Kansas City to have an MRI done. Infante had already lost his starting second baseman job to Ben Zobrist, but was expected to be on the post-season roster as a reserve infielder, and had begun to heat up with the bat with a seven-RBI performance on Thursday against Cleveland. On the year, Infante was hitting .220/.234/.318 with 2 HR 44 RBI in 124 games.

An oblique strain caused Nationals pitcher Stephen Strasburg, Blue Jays third baseman Brett Lawrie, and Rays first baseman James Loney to each miss a month with an oblique injury, and Giants outfielder Hunter Pence has already missed a month without returning to the lineup.

The injury improves the chances of Christian Colon earning a spot on the post-season roster as a reserve infielder, as he is the only non-starter on the roster who can play middle infield. The Royals have not ruled out promoting another infielder to the roster, such as top prospect Raul Mondesi. Mondesi is not on the 40-man roster, so the Royals would have to open up a spot for him. They can not place Omar Infante on the 60-day disabled list to make room on the roster, since Infante will not spend 60 days on the disabled list. Infante has two years left on his contract, with a club option for 2018.

The Royals also promoted right-handed pitcher Michael Mariot on Saturday to help the bullpen.