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4/13/2013 7:38 P.M. ET

Wandy throws pain-free, sets target return date

PITTSBURGH -- Standing in short left field, Wandy Rodriguez appeared comfortable playing catch early Saturday afternoon. He showed no apparent signs of a left hamstring strain that has temporarily knocked him out of the Pirates' rotation.

It was not an illusion. The lefty later said that throwing a baseball isn't a problem, what immediately follows is.

"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.

Irwin joins Pirates in advance of Sunday's debut

PITTSBURGH -- Right-hander Phil Irwin joined the Pirates on Saturday -- not yet on their roster, but on their taxi squad, set to make his Major League debut by starting Sunday against the Reds.

Irwin will step in for left-hander Wandy Rodriguez, whose left-hamstring strain will prevent him from making the start, but is not serious enough to warrant placement on the disabled list. The Pirates cannot formally announce that move until Irwin is placed on the 25-man roster. A corresponding move for him will be made after Saturday night's game.

Irwin participated in pregame workouts Saturday, but could not be in uniform for the game against the Reds. A new rule in the latest Collective Bargaining Agreement formally revives the NFL's old taxi-squad concept -- it even officially goes by that name -- of openly allowing extra players in the event of an injury-forced need. Previously, teams clandestinely preparing for possible emergencies by recalling players would have to keep them out of sight.

Irwin, a 26-year-old right-hander taken in the 21st round of the 2009 First-Year Player Draft, underscored his development with an impressive Spring Training. The Yankees roughed him up on March 17 in his final outing prior to being optioned to Triple-A Indianapolis, but he allowed five hits in eight innings, striking out nine, before that.

Irwin allowed one run in six innings in his only Triple-A start this year. Last season, Irwin rose from Class A all the way to Triple-A, with a composite record of 8-7 and 2.83 ERA on the three rungs.

"He's made real good improvement," manager Clint Hurdle said. "He can bring us the best package for competing right now."

Worth noting

• Irwin will wear No. 36 for the Pirates after wearing No. 57 in Spring Training.

• Pedro Alvarez (0-for-24) and Clint Barmes (0-for-17) both snapped long hitless streaks in the Bucs' season-high 12-hit win Friday night. However, the low man on the batting totem pole remains Russell Martin, who was 2-for-31 entering Saturday night's game.

Number to note

.700: Starling Marte's on-base percentage leading off games entering Saturday's action. He has six hits in his first nine at-bats and also drew a walk.

Quote to note

"It means a lot. It'll be cool. It shows how good those guys with 3,000 are. I've been around a long time and I'm just sniffing 2,000."
-- A.J. Burnett, who will make his next start with 1,998 career strikeouts, looking forward to 2,000

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.