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7/27/2013 12:45 A.M. ET

Clippard riding impressive scoreless streak

WASHINGTON -- The Nationals' bullpen has seen its fair share of struggles this season, but Tyler Clippard has been nothing short of dominant.

Clippard pitched his 14th consecutive scoreless inning on Friday against the Mets and is 3-0 with a 0.41 ERA since June 1. Entering Friday's doubleheader, he was holding opposing hitters to a .133 batting average, the best of any National League relief pitcher with more than 15 appearances.

"I know this year, in comparison to last year, I've really tried to focus on pitching more," Clippard said. "I feel like I got away from that a little bit last year, especially toward the end of the year, where I kind of became too one-dimensional. I've really focused on putting together my full repertoire in each outing, and the more I do that, the more comfortable I feel doing that."

When pitching in big situations early last season, Clippard said that he relied heavily on his fastball and changeup. He wanted to beat hitters with his best stuff, so he neglected some of his breaking pitches, and as the season progressed, he struggled to incorporate those secondary pitches again.

"It was kind of a snowball effect, and I got away from it completely," the 28-year-old said. "So I came into Spring Training this year really focused on being able to bring those pitches back into my repertoire more frequently, because I know that that's how I've always had success in my career."

Clippard has mostly pitched the eighth inning this season and ranks third in the NL with 18 holds. While that regularity has helped him figure out a routine and mentally prepare for each outing, Clippard said that he pitches the same way every time, regardless of what inning it is. Shortstop Ian Desmond agreed.

"I don't look at him as an eighth-inning guy. I look at him more like an end-of-the-game type of guy, a finisher in that seventh, eighth, ninth," Desmond said. "He'll do a great job in any role."

Nats reliever Mattheus hopes to contribute

WASHINGTON -- Ryan Mattheus officially rejoined the Nationals on Friday morning as the allotted 26th man for their doubleheader against the Mets. He used his previously broken right hand to exchange handshakes with teammates and said that he couldn't be any more excited to be back.

"It's amazing," Mattheus said before the doubleheader. "It was a long time off. It's tough to sit back and watch the games from that perspective, and it's just great to know that I can go out there and contribute today."

After punching his locker in May and missing 58 games, Mattheus returned to the mound at Nationals Park in Friday's matinee. He walked two and allowed three earned runs while recording four outs.

While added as the 26th man for the doubleheader, Mattheus will stay with the club after the Nationals optioned struggling reliever Drew Storen to Triple-A Syracuse.

"I just don't know what it was," he said after the Nationals' 11-0 loss. "I didn't feel too pumped up. I did a pretty good job of settling myself down. It could be mechanical. I got a little short on a couple sinkers, bounced them in the dirt. Then I started feeling for stuff. I made some good pitches, then I made some not-so-good pitches. We'll move forward from there."

Mattheus had a cumulative 2.25 ERA in six rehab appearances, including stops at three of the organization's four Minor League affiliates. He said that he hasn't had any soreness in his hand throughout the rehab process and is throwing all of his pitches with regular velocity and control.

Mattheus wasn't particularly strong in his first appearance in two months, but he'll have more opportunities to prove himself moving forward.

"It's awesome," he said of rejoining the team. "I just wish we could have won the ballgame and I could have performed a little better."

Worth noting

• Johnson decided to stick with Steve Lombardozzi at second base in the first game of Friday's doubleheader against the Mets. He said that regular second baseman Anthony Rendon would start the nightcap.

"I'm not changing a winning hand right now," Johnson said.

Tom Schad is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.