The Pirates¡¯ growing list of injuries grew even larger in Wednesday¡¯s game against the Cardinals.

Starter Trevor Cahill exited Pittsburgh's 8-5 loss at Busch Stadium with left calf discomfort in the second inning, the Pirates announced. He¡¯s listed as day to day.

Cahill was struggling to begin the frame. After two consecutive walks, he threw a curveball that hit Edmundo Sosa to fill the bases, then threw a first-pitch sinker to Cardinals starter Jack Flaherty that missed wide to the outside portion of the plate. The right-hander, who usually comes set in a fielding position after firing a pitch, hopped from one foot to the other in visible discomfort, and athletic trainer Rafael Freitas emerged from the dugout to check on Cahill.

¡°I think we noticed it two pitches before that,¡± manager Derek Shelton said. ¡°When he landed, it just didn't look right. And then the next pitch after that, [he] started to walk around and shake it out a little bit.¡±

The conversation didn¡¯t last long, as Cahill walked off the mound and was visibly frustrated as he entered the dugout.?

¡°I was making adjustments,¡± Cahill said. ¡°I was able to find my way, but it got to the point where I couldn¡¯t go any more.¡±

Duane Underwood Jr. came on in relief and allowed five runners to score that inning, three of which were charged to Cahill, before settling down to complete three innings.

¡°It¡¯s one of the tougher situations a pitcher can come into: bases loaded, nobody out,¡± Shelton said. ¡°After that, he executed some breaking balls and actually pitched [like] what we expected.¡±

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A potential loss of Cahill would hurt a pitching group that is already down a few starters. Steven Brault (lat) is on the 60-day injured list while throwing in Bradenton, Fla., and Chad Kuhl (shoulder) is on the 10-day injured list. Though Kuhl is nearing a return and the team has an off-day Monday, the Pirates won¡¯t fill a potential hole by activating Kuhl.

Kuhl, Pittsburgh¡¯s Opening Day starter, pitched three innings in his first rehab start at Triple-A Indianapolis on Wednesday night, limiting the St. Paul Saints to one hit and one walk. However, Shelton said that the Pirates want to see the right-hander -- who went on the injured list on April 22 with right shoulder discomfort -- recover and get more work.

¡°As we've always talked about, tomorrow's the most important day,¡± Shelton said, ¡°because he pitched, and then [it¡¯s about] how he feels and goes about it. He will have another rehab start.¡±

There are other options for the Pirates, including No. 12 prospect Miguel Yajure. General manager Ben Cherington has said that the club will look for good opportunities to put Yajure into the Major League mix and get his feet wet as a starter.

¡°What we¡¯re trying to do with Miguel -- and maybe others as well, as we get into the season -- is pick spots to bring guys in and give them a chance to make Major League starts,¡± Cherington said on his show on 93.7 The Fan on Sunday. ¡°Hopefully, there¡¯s a dual benefit to that, that they get that experience and development opportunity, but also, occasionally, we¡¯ll use that to pick a time to push back the rest of the guys to give [them] an extra day of rest.¡±

There are two potential issues with that route, though. First, it may not make sense to pick now as a time to bring in Yajure, as he just entered the rotation for a spot start Friday that pushed the rotation back. Also, with the off-day Monday, the Pirates have more time to work with, and they could always opt for a bullpen game with a couple of long options in Underwood, Luis Oviedo and Chris Stratton.

However, Yajure¡¯s outing certainly justifies another start sooner than later, as he held the Giants scoreless on one hit and one walk over five innings last Friday. The Pirates also have another starting option with MLB experience in Chase De Jong, who has a 4.50 ERA in three starts this season at Triple-A.

For the time being, the Pirates are hoping that Cahill will be back sooner than later, and they¡¯re leaving next week¡¯s rotation decisions until then. It¡¯s a tough location to be injured, as the calf issue is on the leg that Cahill plants into the mound when he follows through.

¡°It¡¯s just something that I couldn¡¯t get through,¡± Cahill said. ¡°Hopefully it¡¯s nothing serious.¡±

The Pirates are ready to grind to pick him up, as they¡¯ve tried to pick up injured player upon injured player in the early going.

¡°It¡¯s tough, but we have to fight like we did today -- we fight, no matter what happens,¡± said Gregory Polanco, who homered Wednesday. ¡°We¡¯ve got to stay in the game.¡±