"It came pretty quickly, and I started to get some spasms," he said after the game. "So we decided to just shut down and get some treatment. All the strength tests seemed fine, so we'll see how it is [Wednesday]."
It was the first time Mercer has missed a start since Aug. 26. The 28-year-old has appeared in 138 of the Pirates' 150 games this season, hitting .264/.311/.397 with 11 home runs and 53 RBIs.
Barmes came off the disabled list last month (left groin strain) and went 1-for-3 with a single Tuesday, raising his average to .232.
• A limited number of tickets to possible NL Wild Card and Division Series games at PNC Park will go on sale Thursday at 10 a.m. ET. The sale of tickets, maximum of four to each possible game, can be purchased at www.pirates.com/postseason or by phone (1-877-893-BUCS). Fans coming to the PNC Park main box office will receive a wristband number to be distributed starting at 7 a.m., and positions in line will be determined by a random drawing of matching numbers.
Stephen Pianovich is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.