Nationals cleanup hitter Michael Morse underwent a second treatment for his strained right lat, perhaps a platelet-rich plasma injection, and his status for opening day is in question, Manager Davey Johnson said.

(Julio Cortez/AP)

 The Nationals first discovered Morse’s strained lat March 6, after he told team trainers of discomfort around the bottom of his right shoulder blade. On March 10, he received a cortisone shot. Morse served as the Nationals’ designated hitter March 12 and 13, but he has not played in the field since his diagnosis. Morse began playing catch a few days after his injury, but could not extend beyond 90 feet. On Tuesday, the Nationals instructed Morse to participate in no baseball activity for a week.

The Nationals at first said publicly Morse would miss only a handful of days, and Morse said – and has continued to say – he is not worried about the injury. But Johnson said the Nationals are neither discounting nor counting on Morse playing opening day.

“To be clear,” Johnson said, “it’s really unclear.”

Meanwhile, Nationals closer Drew Storen was sent for tests on his right arm, Johnson said. He had experienced soreness in his triceps and biceps and also missed several days with strep throat. Storen felt more discomfort while he played catch yesterday. He has not pitched in a game in more than two weeks, and Johnson did not have a timetable for his return.

“The way he pitches, his arm is in tremendous shape,” Johnson said. “His velocity, his movement. He threw a lot of innings last year. He builds up a lot of innings, throwing a lot, not in the closer role early. And he’s my closer. With him, I want to make sure he’s 100 percent healthy and he doesn’t do too much, because he’s going to be my closer. And the way he’s throwing, he’s a throwaholic. He likes to throw. Hard. We’re just going to be very cautious on him. None of these guys, when they do play, that it’s going to exacerbate the injury.”

The Nationals are also monitoring Adam LaRoche’s sprained foot and Chien-Ming Wang’s pulled hamstring. But they are most concerned with Morse, their best offensive player last season. Johnson hoped for more clarity from team doctors by Sunday, when the Nationals end a three-game road trip, but he felt more confident in LaRoche than Morse.

“It’s probably more iffy with [Morse and Wang] to open the season,” Johnson said.

Johnson has been encouraged by Morse’s assertion that he feels fine, but also discussed contingency plans for Morse’s absence in left field. He expects Mark DeRosa will begin playing more in left field this spring, and infielder Steve Lombardozzi appeared in the outfield Wednesday for the first time in his career.

Over the weekend, the Nationals signed veteran outfielder Xavier Nady to a minor league contract, and he will play in a minor league game today, his first action with the Nationals. If Morse begins the season sidelined, it will open another spot for one of Brett Carroll, Jason Michaels or Chad Tracy, the three players currently competing for the final bench spot. Morse’s absence could also give Rick Ankiel or Roger Bernadina more time in the starting lineup.

Johnson was unclear in describing the treatment Morse recently underwent, but said he believed the slugger had undergone a PRP, or platelet-rich plasma, injection. He called it an “aggressive treatment to help it heal.”

“Then you look at it a week after that treatment,” Johnson said. “He had something to promote healing, and I think it was that – his own blood.”

The platelet-rich plasma therapy is a relatively new treatment for muscle sprains and strains. Doctors remove about 30 milliliters of the patient’s blood and spin the blood in a machine, which separates out the platelet-rich plasma from the blood. The doctors then inject the plasma into the affected muscle in order, in theory, to promote tissue recovery.

Many high-profile athletes, including Tiger Woods, have used the procedure. New York Yankees third baseman Alex Rodriguez used PRP therapy in 2009 while recovering from a torn labrum in his hip, and again this offseason to strengthen his shoulder and knee. Orioles left-hander Zach Britton underwent the procedure yesterday to heal a shoulder injury.

 The merits of the treatment are still being debated. The British Journal of Sports Medicine released a study last year that found patients who used PRP and a placebo treatment experienced similar results in healing an Achilles tendon injury.