(Justin Edmonds/GETTY IMAGES)

Mattheus used his full repertoire in a 25-pitch bullpen session this morning, and he felt a vast difference from before the Nationals ordered him to rest. Mattheus, who had been playing long toss, was throwing his fastball roughly 89 miles per hour before his time off, about six less than his usual velocity.

“I definitely feel a lot fresher than I did before,” Mattheus said. “The ball was coming out really good. I’ve had 15 days off, so I didn’t expect anything less. I’m happy with it.”

Between the minors and majors, Mattheus has appeared in 54 games this year, his first full season after returning from Tommy John surgery. He appeared in 29 games in 2009 and 2010 combined because of his ligament-replacement operation. Mattheus did not realize the sharp increase in his workload until pitching coach Steve McCatty alerted him.

“It was definitely the right thing,” Mattheus said. “There was something going on. I don’t know exactly what it was. I can’t pinpoint it. The workload I’ve had this year has been a pretty good amount. … They just wanted to give me a breather, revamp everything, get me feeling good again.”

Mattheus will play long toss tomorrow and throw and, if all goes well, another bullpen session Tuesday. If Mattheus stays on the plan laid out by the Nationals, he should return Sept. 20.