Eric Hartline-USA TODAY Sports

In Aaron Barrett, the Nationals summoned a September call-up who is not a typical September call-up. He did not come to the majors as a green rookie the Nationals want for emergencies, or to give him a taste of the majors. Barrett played a crucial role for the Nationals’ bullpen for much of the season, and after a month at Class AAA Syracuse, Barrett has returned to again provide a key dimension for the Nationals’ relief corps.

In his rookie season, Barrett made the Nationals’ opening day roster with an excellent spring training. Manager Matt Williams relied on him for high-leverage outs against some of the best right-handed hitters in the National League. In 40 appearances, Barrett punched up a 3.21 ERA and struck out 11.5 batters per nine innings. At the end of July, Barrett scuffled, and the Nationals wanted to limit his innings to keep him fresh. After a fruitful month at Syracuse, Barrett will return to the same role he had before.

“He had gone into unchartered territory a little bit, so we wanted to back him off,” Williams said. “We allowed him to have a more regular schedule and just keep him fresh. He’s full-go right now. He’ll serve the same role as he did before. He’ll come in and be our wipeout righty. He’s fresh and he’s ready, which is good. We need him.”

Barrett used his time well at Syracuse, where he allowed no runs, five hits and one walk in 10 1/3 innings. He worked on a set schedule, so he never warmed up unless he entered the game. He had a hiccup with his delivery after umpire Joe West called a balk on him, and he smoothed it out by making an adjustment to the way he sets his hands.

“You don’t want to get sent out,” Barrett said. “It was a little bit of disappointment. At the same time, I was able to get some rest and continue to work on some things. Initially, you’re a little disappointed. But you understand that you’re not in control of it. You just do what you’re told, and you got to keep working.”

Barrett also refined his change-up and added it to his repertoire. He tweaked the grip he uses, and the time in the minors allowed him to throw it in games and gain confidence. Barrett never threw the pitch in the majors, but it could have an effect. Barrett’s already vicious slider will become even tougher on hitters if they have to worry about a change-up that breaks the other way.

“It gave me a pitch I can actually use,” Barrett said. “I’m looking forward to using it.”

Williams could use Barrett and left-handed call-up Xavier Cedeno as a right-left tandem. At Class AAA, left-handed batters hit .135 with a .384 OPS against Cedeno this season.

“He’s more situational,” Williams said. “We’ll use him to come in and out. That opportunity presents itself all the time in the sixth, when you’ve got two outs. You’ve got a lefty and then a righty, you can get [Cedeno and Barrett] hot to get through the sixth and set up our bullpen.”

If the Nationals’ starter wanes in  the sixth inning, against a key spot in the order, Williams could call on either Barrett or Cedeno – or both, depending on  the lineup construction – to escape the situation. And he wouldn’t need to use any of his well-used back-end relievers.

“That’s the beauty of having all these guys in September,” Williams said. “You have more bullets. And they’ve both done it. It’s not foreign to them.”