Pitcher Ryan Mattheus (Associated Press)

Ryan Mattheus is in Viera, Fla., at the Nationals spring training complex throwing bullpen sessions and facing hitters, according to Nationals Manager Davey Johnson. Mattheus, who broke his hand on May 19, started throwing off the mound last week and is ramping up his throwing program ahead of an upcoming rehab assignment.

Mattheus, 29, was ahead of schedule when he jumped back on the mound for his first bullpen session last Friday. He performed well and moved his throwing to Florida while the team left for a seven-game road trip to Philadelphia and Miami.

After allowing five earned runs in an inning in San Diego two months ago, Mattheus punched his locker with his throwing hand and broke a bone, a lapse in judgement for which he has since apologized. Mattheus had a 4.96 ERA in 16 1/3 innings and is an important piece of the bullpen. He posted a 2.85 ERA in 66 1/3 innings in 2012 and 2.81 ERA in 32 innings the previous season. He is also under team control until 2018.

When he is ready, Mattheus will force the Nationals to make a difficult decision about the composition of their bullpen. They overhauled their bullpen recently, adding left-handers Ian Krol and Fernando Abad and long reliever Ross Ohlendorf, and it has performed well.

Another reliever viewed as an key piece of the bullpen before the season suffered another setback in his rehab from a spring training injury. Christian Garcia, 27, was at Class AAA Syracuse on a rehab assignment from a partially torn right forearm tendon he suffered in spring training.

But while rehabbing, he felt some shoulder soreness and was shut down. After he returned from that on June 25, he recently experienced hamstring issues, Johnson said.. He received an MRI and the recent setback only further delays his return. Garcia impressed last season in his September call-up with 2.13 ERA 12 2/3 innings and with a high-90s fastball and filthy change-up.