SAN DIEGO -- Nationals third baseman Ryan Zimmerman didn't play in his fourth consecutive game Thursday because of a sore left shoulder, but manager Manny Acta continues to say the shoulder is getting better. Zimmerman is listed as day-to-day, and there is no timetable as to when he will return to action.

Zimmerman missed the entire three-game series against the Padres, and it's not known if he will play in the Nats' upcoming three-game series against the Diamondbacks, which begins Friday.

"He is feeling much better -- as soon as he is ready to play, he will play," Acta said.

Zimmerman said the Nats' doctor told him there was no structural damage in the shoulder. Zimmerman had been playing about a week with the sore shoulder. He hurt it on May 18 against the Orioles, sliding headfirst into second base.

"I'm trying to get better. I'm feeling better," Zimmerman said. "Everything is still going good."

Meanwhile, closer Chad Cordero, who is on the disabled list with a torn right shoulder adductor, is traveling with the Nationals and appeared with catcher Paul Lo Duca and broadcaster Johnny Holliday calling Thursday's game on the Mid-Atlantic Sports Network.

Cordero is throwing on flat ground every other day and is not feeling any soreness or pain. On Wednesday, he threw 60 pitches from 75 feet. On Friday, Cordero is expected to throw from 90 feet.

Cordero hops to be back in action by the end of June.