Quartet of hurlers working way back to mound

SARASOTA, Fla. -- As encouraging as the Pirates' spring pitching has been -- their allowance of 5.2 runs per exhibition is among the Grapefruit League's lowest -- club officials are also enthused by four arms on the back burner.

Jeff Karstens is not as far back as the other three, as he completes rehabbing from biceps tendinitis. He is due to throw a bullpen session on Monday, after which pitching coach Ray Searage will look for a spot for his preseason debut.

Charlie Morton is set to throw 20 pitches of batting practice on Monday, the first time he will have faced hitters since May 29, when he was shut down and given a June 10 appointment for Tommy John surgery.

Left-hander Francisco Liriano (fractured right arm) also continues to make gradual progress in his limited throwing program.

Then there is Jose Contreras, who is squirreled away for midseason bullpen help and is another Tommy John surgery patient whose recovery is actually ahead of Morton's.

"This will be good for Charlie," Pittsburgh GM Neal Huntington said of the righty's upcoming BP session. "He's anxious to compete with someone beyond himself.

"Liriano is about where we expected him to be. With that big heavy cast he had on for a long time, there was more atrophy in the right arm than we anticipated, but he remains on schedule, and is champing at the bit to begin competing."

Despite the fact Karstens will miss about three weeks of exhibition play, Huntington still considers him "on track" to be a part of the season-opening rotation.

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.