Boyle, who was lifted after one inning in Sunday's loss to the Marlins, was suffering from lower-back pain that got worse the more he threw during the frame, MLB.com reports.

Advice: Boyle's performance clearly seemed to be affected by his physical limitations, as he allowed four earned runs on a hit and three walks over his sole inning on the mound. Manager Mark Kotsay confirmed Boyle would undergo an MRI on Monday to determine the severity of the injury, at which point the right-hander's chances of making his next scheduled start Saturday against the Mariners will become clearer. Per Sonja Chen of MLB.com, right-handers Osvaldo Bido and Joey Estes, both of whom have big-league experience and are on the 40-man roster, are candidates to be called up from Triple-A Las Vegas should Boyle miss at least one turn through the rotation, although she adds Oakland has long relievers Mitch Spence and Kyle Muller as options on the big-league roster. Rotowire.com 33 minutes ago

Gallegos (2-1) failed to record an out Sunday versus the White Sox, allowing three runs on three hits to take the loss.

Advice: Gallegos hadn't pitched since allowing four runs without recording an out versus the Tigers on Tuesday. He was already on shaky ground before this recent stretch of dreadful pitching -- Sunday's outing puts him at a 12.00 ERA and 2.33 WHIP with a 13:7 K:BB over nine innings this season. He's still managed a save and two holds, but Gallegos has been leapfrogged by Andrew Kittredge and JoJo Romero for high-leverage duty in the Cardinals' bullpen. Rotowire.com Today, 8:56 pm

Peralta (3-1) allowed three runs on three hits and six walks over five innings Sunday, striking out five and taking a loss against the Cubs.

Advice: Despite the command issues all afternoon, Peralta kept the Cubs off the board until coughing up three runs in the fifth inning. He took his first loss of the year and has now failed to complete six frames in three straight outings. During that stretch, he's posted a 6.00 ERA with a 17:11 K:BB. Peralta forced 13 whiffs Sunday but threw just 51 of 97 pitches for strikes. His season ERA climbed to 3.49 through 38.2 frames. As of now, it's unclear when Peralta will make his next start, as the decision on his pending suspension still needs to be determined. Rotowire.com Today, 8:19 pm