Sun 5/17/15 12:28 PM

Manager Ned Yost confirmed that Duffy would make his next scheduled start Saturday against the Cardinals, but noted that the lefty needs to show improvement in order to maintain his spot in the rotation, MLB.com's Jeffrey Flanagan reports. Duffy entered the season with high expectations after posting a 2.53 ERA and 1.11 WHIP across 149.1 innings last season, but he's largely struggled to replicate that success. Though his strikeout rate is up from a year ago, Duffy's control has betrayed him, as his walk rate sits at an unpalatable 10.7 percent. The control issues, coupled with a .293 batting average against -- up nearly 90 points from a year earlier -- have put Duffy's job on notice with Jason Vargas (elbow) due to return from the DL soon. Since Duffy still has minor-league options remaining, he'd likely be the most vulnerable to losing a rotation spot if he's unable to turn things around during Saturday's start.