(Nati Harnik/AP)

“Sometimes, it moves a little bit,” Purke said. “I just try to keep around the plate, and whatever it wants to do, it does.”

Purke threw an impressive bullpen session Friday, earning nods of approval from pitching coach Steve McCatty as he watched from behind the mound. Purke knows he will not break camp as a major leaguer, that he’ll spend the majority of his spring on the minor league side of camp.

Purke is just happy to be healthy, to start a season “clean,” he said, not scrambling to get innings in without it not hurting.” In the fall of 2010, Purke first started feeling pain in his left shoulder. His shoulder started feeling better in the spring, but a massive blister on his finger sidelined him. When he returned, his shoulder started hurting again, and he missed 11 starts, almost the whole season.

Purke finished the season and was confident his ailment had been bursitis, an injury that would not leave any lingering structural problems. He let the Nationals perform an advanced MRI exam that included injecting dye into his shoulder, and team doctors came away convinced Purke would have no long-term physical issues.

“Totally good now,” Purke said. “Once I got through the middle of my offseason last year, I was coming back from it in the summer. Everything started to come back. It’s been months with no pain.”

When Purke pitched with pain, he later realized, he dropped the angle of his arm to avoid putting pressure on his shoulder. Since regaining health, Purke has returned to his original arm slot, a unique position somewhere between three-quarters and sidearm. He said the arm position had nothing to do with his bursitis, and General Manager Mike Rizzo agreed.

“I like his slot,” Rizzo said. “It’s a funky slot that hitters aren’t used to seeing.”

● Edwin Jackson threw his second bullpen session of the spring, giving those watching another chance to dissect whether or not he hid the ball in his delivery, or if he was tipping his pitches. Jackson already (and understandably) has grown a little weary of the topic, and said it’s not a new process he’s starting this spring.

“I just got to get everybody to understand, it’s not just this year I changed my mechanics,” Jackson said. “I started changing mechanics last year. When I got to St. Louis [at the trade deadline], I started going over my head. By my fourth start, I wasn’t going over my head. At this point, it’s not even really a mechanical thing. It’s finding a consistent delivery.

“Whether it’s dropping below my glove, whether it’s tipping, it’s just the fact of having consistency in what you’re doing. You could hide the ball more. At the end of the day, it’s about finding a consistent delivery, throwing strikes, locating the ball where you want it.”

● Henry Rodriguez, who arrived late because of a personal matter, did not throw a bullpen session today, as Manager Davey Johnson expected him to. Instead, the Nationals wanted to let Rodriguez play catch for two more days before stepping on the mound in order to avoid what happened last year. Rodriguez arrived late to camp last spring because of a visa issue, and when he started throwing he injured his neck, an ailment that derailed the first portion of his season. He said his arm feels good now.

More on Nationals spring training:

Zimmerman looking for security in contract negotiations

Lidge embraces new role in bullpen

Nats map out Grapefruit League rotation

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