KANSAS CITY, Mo. — The ace of the Kansas City Royals pitching staff is working to return to the lineup.

After almost two weeks on the 15-day injured list with a right flexor strain, starting pitcher Zack Greinke will begin his rehab assignment in Omaha on Sunday.

Greinke will pitch for the Royals AAA affiliate Omaha Storm Chasers.

If Greinke only needs a single rehab start, he could start as soon as next Friday against the Oakland A’s.

This season, Greinke is 0-4 in 10 starts with a 5.05 ERA and 25 strikeouts.