Brian Fuentes's stay with the Cardinals has been a brief one. (Getty Images)

Lefty reliever Brian Fuentes, who's just 5.0 innings into his Cardinals career, has been placed on the restricted list. FOXSports Midwest's B.J. Rains reports that Fuentes informed the team that he "needed to step away from the game for personal reasons."

According to St. Louis manager Mike Matheny, Fuentes is unlikely to pitch again this season (FS Midwest).

The Cardinals have replaced Fuentes on the active roster with right-handed reliever Trevor Rosenthal. Rosenthal was called up briefly earlier this season, but he's spent the vast majority of 2012 at the Double-A and Triple-A levels, where he has a combined 3.12 ERA and 96 strikeouts in 104.0 innings.

Per terms of the restricted list, the 37-year-old Fuentes, should he decide to pitch again, would report to the Cardinals or find another team willing to trade for his rights.

For more baseball news, rumors and analysis, follow @EyeOnBaseball on Twitter, subscribe to the RSS feed and "like" us on Facebook.