The St. Louis Cardinals' starting rotation has already been stretched thin since the trade deadline, but it just suffered a major blow.

The Cardinals made the right decision to sell at the trade deadline despite their success this season, trading Dustin May and JoJo Romero to the Milwaukee Brewers to bolster their farm system, but it left their rotation with less depth. With May gone, St. Louis turned to second-year pitcher Hunter Dobbins to fill the void left behind in its rotation.

Dobbins has had mixed success with the Cardinals this season, but unfortunately was forced to exit Friday's game against the Philadelphia Phillies after only four innings, throwing just one pitch in the fifth inning due to right forearm tightness, as reported by Derrick Goold of the St. Louis Post-Dispatch.

Dobbins forced to exit Friday's game early

The Cardinals acquired Dobbins during the offseason in a blockbuster trade with the Boston Red Sox in exchange for Willson Contreras. The 26-year-old made 13 appearances with the Red Sox in his rookie season, including 11 starts, posting a 4.13 ERA and striking out 45 batters over 61 innings pitched.

Dobbins has performed better this season despite not having a consistent role in the Cardinals' starting rotation. He spent a large portion of the year moving back and forth between St. Louis and Triple-A Memphis, or pitching in a bulk-relief role. Dobbins has gone 3-3 through 10 games this year in St. Louis, including seven starts, with a 3.42 ERA and 49 strikeouts.

Dobbins' injury is just the most recent in a slew of injuries the team has been dealing with. St. Louis placed Ixan Henderson on the 60-day injured list with a left elbow strain only a few days ago, and took another blow by placing Andre Pallante on the 15-day injured list on Friday with right elbow inflammation.

Trading May away at the trade deadline gave Dobbins the perfect opportunity to step into a steady starting role and develop further in his second season in the big leagues. It's unfortunate he was forced off after only three starts in the new role, though the severity of his injury remains unclear.

Losing Dobbins for a significant time would be a massive blow to the Cardinals, especially considering the other recent pitching injuries. St. Louis is only a few games out of a playoff spot, but it would be hard to make a push down the stretch if the pitching staff is dealt another significant blow with Dobbins, unless it looks elsewhere to add another hurler.