Pirates manager Clint Hurdle didn't term Walker's back as "flared up," but wanted to give the second baseman a break after the past two games. Saturday's contest lasted three hours and 26 minutes, while Sunday's was a Pirates' season-long four hours and four minutes.
Brook Holt started in Walker's place at second, batting eighth.
Walker missed 16 games with lower back tightness before making a pinch-hit appearance on Friday and started and played full games Saturday and Sunday. Hurdle said he wanted to give Walker a break after the second baseman didn't do much of anything the prior two weeks.
"Back-to-back games, they were extremely long games, a long time spent on his feet," Hurdle said. "He can give us what we had, but I think we'd be better served to give him the day today and get him back in for the Milwaukee series," Hurdle said.
Hurdle said Walker would be available off the bench on Monday.