"Based on the way he responded last night, that there was some tightening up, we thought we'd give him a full day of treatment," Pirates manager Clint Hurdle said of his second baseman.
Hurdle didn't have a definitive answer as to if Walker would be available for Wednesday night's game. But the second baseman did not take batting practice with the team on the field, and it seemed unlikely he would play.
In addition to Walker's back trouble, center fielder Andrew McCutchen remains off the disabled list, but sidelined with a fractured rib on his left side. Already working with a patchwork lineup, Hurdle would have just three position players -- Gaby Sanchez, Jayson Nix and Chris Stewart -- off his bench vs. Miami if Walker was unavailable.
With Pedro Alvarez on the bereavement list, Wednesday marked the first time McCutchen, Walker and Alvarez were all out of the Bucs' lineup since the trio was on the roster (June 16, 2010).
Stephen Pianovich is an associate reporter for MLB.com.