MILWAUKEE (AP) The Washington Nationals have activated newly acquired reliever David Carpenter after placing right-hander Aaron Barrett on the 15-day disabled list with a strained right bicep.
The Nationals made the moves before Friday's game against the Milwaukee Brewers.
Barrett left Thursday game against Milwaukee in the middle of an at-bat by Hernan Perez in the eighth inning. Barrett took the loss after giving up the go-ahead single to Milwaukee's Scooter Gennett with two outs.
Nationals manager Matt Williams said the right-hander was headed back to Washington for additional medical attention.
''He's going to go see (team physician) Wiemi (Douoguih) and get some tests done,'' Williams said. ''The preliminary is that he's got a biceps strain.''
Barrett is 3-2 with a 4.64 ERA in 30 games this season.
''We want to make sure we calm it down, heal him up and get him back here,'' Williams said.
Carpenter was acquired from the New York Yankees on Thursday for minor league infielder Tony Renda. The reliever was designated for assignment by the Yankees on June 3.
Carpenter is returning to the NL East after spending the 2013 and 2014 seasons with Atlanta.