"I can do everything -- run, throw -- but I feel a little something on my follow-through," Rodriguez said, indicating the trouble spot as the inside of his left thigh. "When I drag my left leg after the delivery, there's tightness there."
The Pirates will skip Rodriguez's next turn in the rotation, which would have come Sunday in the series finale against the Reds. Phil Irwin will step in and make his Major League debut. Rodriguez has already been tentatively penciled in to make his return start April 19 against the Braves.
Although that game is 11 days after his start Monday in Arizona, manager Clint Hurdle said it is an "improbability" that Rodriguez will go on the 15-day disabled list.
"He's making progress. The window is short enough that if he misses one start, he could make the next one without a hiccup," Hurdle said. "We also have to consider the [Jeff] Karstens situation."
Karstens experienced tightness in his right groin a year ago in an Aug. 25 start, but was back on the mound for his next turn in the rotation. He threw only one inning before experiencing a right hip flexor injury and did not start again.
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.