Wang, who will be a long reliever, was slated to be the fifth starter in Washington's rotation, but he started the season on the DL because of a strained left hamstring. He said last week that he was willing to work out of the bullpen as long as the team gave him advance warning so he could prepare. Wang has worked out of the bullpen five times during his career, all coming when he pitched for the Yankees.
"The team has given me this opportunity, and I would like to try my best, try to get the job done, try to help the team win," Wang said before Tuesday's game.
Manager Davey Johnson said that he will treat Wang like a starter, which means he could pitch in his first game of the season on Friday against the Braves. Left-hander Ross Detwiler had a similar schedule last year when he was a long reliever.
"Tuesday is a bullpen session. I would probably treat him like I would a young starting pitcher," Johnson said. "I will probably try to keep him on the same throwing schedule he is on. He will set up to pitch in his regular rotation on Friday. I'll probably hold him for that day."
Mattheus is being shelved because of plantar fasciitis. According to MLB.com's Paul Hagen, Mattheus started to feel discomfort in his left foot while running in the outfield before Monday night's game against the Phillies and was not available to pitch.
Mattheus had an X-ray and saw a foot specialist in Baltimore on Tuesday. He will wear a boot for at least two weeks. Mattheus has been a productive pitcher this season, going 2-1 with a 2.25 ERA in 19 games.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.