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8/1/2014 11:58 P.M. ET

Barrett sent to Triple-A to work out some kinks

WASHINGTON -- After a rocky July interrupted his stellar rookie season, Nationals reliever Aaron Barrett was optioned to Triple-A Syracuse before Friday night's game against the Phillies to open a roster spot for newcomer Asdrubal Cabrera.

Fellow rookie right-hander Blake Treinen, recalled Thursday, will remain in the bullpen to provide an extra long man while Barrett tries to straighten some things out in the Minors.

"Aaron has been in a lot of pressure situations so far, and it's not easy for a first-year pitcher to be in those situations," Nats manager Matt Williams said. "He's pitched really well. But this gives us an opportunity to get him down and work on things and gave him more of a structured environment to pitch in."

In his first 30 appearances through June 27, Barrett sported a 1.67 ERA over 27 innings, allowing 20 hits and 14 walks while striking out 33. Batters hit .213 against him, with a .571 OPS.

Barrett's season seemed to turn in an appearance against the Rockies on June 30, when home-plate umpire Joe West called him for a balk stemming from the same pre-pitch routine he had used since 2011. Forced to alter his delivery, Barrett has allowed 10 runs (seven earned) on nine hits and four walks in his last 6 2/3 innings over 10 games, giving up a .281 average and .830 OPS.

"I don't think it helps," Williams said of the changes Barrett had to make. "We're all creatures of habit and we're all creatures of timing in this game, so if you have your comfort level up and your timing's right, things tend to work out. When something like that is put into the mix, then it disrupts that."

With Barrett gone and Treinen available to eat innings after starting at Syracuse, Williams will have more freedom to deploy righty Craig Stammen and lefty Ross Detwiler earlier in games rather than saving them for potential extra-innings situations.

Meanwhile, Barrett can work on getting settled in his delivery and stay fresh for the stretch run, as he sits only 15 2/3 innings shy of his career high.

"You never want to lose him," Williams said. "But you try to pick the right opportunity to do so, and we felt this was the right opportunity."

In Nats debut, Asdrubal makes slick play at second

WASHINGTON -- A day after being traded to the Nationals, infielder Asdrubal Cabrera arrived at Nationals Park on Friday and introduced himself to the coaching staff, including manager Matt Williams. In his first game with the team, Cabrera started at second base and hit seventh against the Phillies. 

"I'm just going to do my job. I'll try to get better and help the team no matter what," Cabrera said before the Nats' 2-1 loss to the Phillies.

Cabrera went 0-for-4 and made a nice sliding stop to retire Jimmy Rollins in the third inning. His best at-bat came in the second against right-hander Roberto Hernandez. On the first pitch he saw, Cabrera lined hard to first baseman Ryan Howard, who was able to double off Bryce Harper at first base. 

In the ninth, Cabrera had a chance to drive in the tying run, but closer Jonathan Papelbon struck him out on three pitches to end the game. 

Before the game, Cabrera took some early work at second before doing similar fielding drills during batting practice. He said it felt weird at second base, but he felt confident as the game went on. Cabrera has played most of his career at shortstop.   

"If you play shortstop, you can play any position in the infield," Cabrera said. 

Before the trade, Cabrera was hitting .246 with nine home runs and 40 RBIs. He said he was in the trainer's room when Indians manager Terry Francona told him he had been dealt to Washington. For the last three years, Cabrera had a feeling he would be traded. He felt it even more this year because he will be a free agent after the season. 

"As soon as [Francona] came in, I knew something had happened. I'm happy to be here," Cabrera said. "I will try to help the team play hard and help them to win. … It makes me get excited. When you play for a team like the Nationals, it makes me feel good." 

A few minutes after arriving, he told the coaching staff his son, Meyer, was upset about the trade, believing he would not be able to go in the clubhouse like he did with the Indians. But Williams assured Cabrera that his son could come in the clubhouse. 

"We'll certainly invite his son in when he gets here [Saturday] …outfit him with our new [baseball apparel], so he will be excited about that," Williams said.

Worth noting

• Nationals general manager Mike Rizzo confirmed Thursday to Mid Atlantic Sports Network's Bob Carpenter and F.P. Santangelo that third baseman Ryan Zimmerman has a Grade 3 hamstring strain, but did not say how much action he would miss. MLB.com reported Wednesday morning that Zimmerman had suffered the hamstring strain.

Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. Andrew Simon is a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB. This story was not subject to the approval of Major League Baseball or its clubs.