Norris expects to be behind the plate Thursday

OAKLAND -- Derek Norris is still on pace to start at catcher for the A's in Thursday's series finale against the Astros as he continues to recover from back spasms that made standing up a challenge just three days ago.

Norris was available for "emergency use" on Tuesday but did not play, though A's manager Bob Melvin said he was more likely to be a "useable piece" on Wednesday.

Norris caught a bullpen session on Tuesday and felt good after, and he took batting practice prior to Wednesday 's game. Assuming all goes well, Norris will start Thursday to provide an extra right-handed bat against Astros left-handed starter Erik Bedard.

"Obviously, my back's not 100 percent," Norris said. "But I'm able to do every movement without any pain. It's just a little bit of back tightness and that's it."

Melvin opted not to pinch-run for Tuesday's starting catcher, Stephen Vogt, when he reached first base in the ninth inning with the A's trailing by one run, but the A's manager said that was more because of Oakland's limited bench than Norris' health.

Melvin inserted Coco Crisp to pinch-run for first baseman Nate Freiman in the eighth, which resulted in a everyday third baseman Josh Donaldson switching to first base on defense in the ninth and Alberto Callaspo coming into the game to play third base.

"I had no one to pinch-run for him," Melvin said.