This will be Mercer's second stint with the Pirates this year. He was with the Major League club from May 3-13 and hit .258 (8-for-31) with three homers and four RBIs in nine games, including eight starts at second base. He was optioned back to Indianapolis when Neil Walker returned from the disabled list.
Primarily a shortstop, Mercer put together a .210/.265/.371 batting line in 42 games with the Pirates last year. He's posted a .333/.404/.448 line in 26 games for Indianapolis this season.
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.