The second baseman still is dealing with lower-back issues that likely will hamper him the remainder of this season.
He woke up Tuesday feeling great, but, as the game wore on, he played through discomfort. He woke up Wednesday feeling worse, Pirates manager Clint Hurdle said.
It is unlikely Walker will play more than two games in a row the rest of the season.
"It might be every other day," Hurdle said. "It might be two days, then off a day. We're just going to have to take it day by day."
One of the biggest challenges for Walker was to re-engage after nearly three weeks away from the game.
Had the injury occurred earlier in the season, Walker would have been placed on the disabled list and would have been able go on a rehabilitation assignment in the minors.
But with all the affiliates finished for the season, Walker has had to work his way back in against major league pitchers -- and with his team fighting for a playoff spot.
It's been "trial by fire," he said.
Walker also is trying to strengthen some muscle groups that were dormant as he rested.
The on-field results have been promising, but his health hasn't come around completely.
Walker was available off the bench Wednesday, and Hurdle said he anticipated starting him today.
The Pirates also have been managing a hamstring injury to outfielder Travis Snider, who started Wednesday for the second time since aggravating it Sept. 4.
"We've been trying to find him a way back to 100 percent, and we think that we've got him in that place right now," Hurdle said.
Though the team is carrying 36 players on its active roster, managing a couple injuries to regular players has its challenges.
"Sometimes, 85 percent might be all they have, and, if they can give us that, it might be better than 100 percent of somebody else," Hurdle said.
The Pirates entered Wednesday having allowed 137 steals this season, tied for the most in the majors with the San Diego Padres, who have played one more game than the Pirates.
But one statistic separates the two teams more:
The Pirates have caught 14 runners stealing. The Padres have caught 43.
Hurdle said the Pirates were doing a better job with baserunners earlier in the season. But release times for pitchers have increased.
Catchers aren't making accurate throws, and pitchers aren't doing a good job of disrupting runners on first.
As a result, the Pirates have turned far fewer double plays this season -- 2.14 per game -- than in 2011 -- 2.60 per game.
"We're running out of time," Hurdle said.
"It's been all season long we've worked on this and talked about this. The catchers and the pitchers understand. They know when we're getting taken advantage of."
The Pirates recognized nine players from the minor league system for their community involvement as part of the team's Roberto Clemente Day celebrations, which stretched to Wednesday.
Among the players honored with Pirates Community Commitment Program awards were Jeff Clement from Class AAA Indianapolis, now on the active roster, Tim Alderson from Class AA Altoona, Casey Sadler from Class A Bradenton, Zach Von Rosenberg from low-Class A West Virginia and Luis Heredia from short-season Class A State College.
Gavi Nivar, who finished last season with State College, was honored with a community service award of excellence.
It was his fourth Pirates Community Commitment Program award and honored the fact that he had spent more than 250 hours in community service the past four seasons.
Michael Sanserino: firstname.lastname@example.org, 412-263-1722 or on Twitter @msanserino.