SEATTLE -- Rich Harden took a step closer Saturday in getting back into the A's rotation.

The 26-year-old right-hander with a history of back problems has been sitting on the disabled list since April 3 with a strained right shoulder. But he threw a three-inning simulated game Saturday, 50 pitches worth, before the A's game with the Mariners.

"It felt good," Harden said. "We'll know more in the next couple days."

The first thing he wants to know is how he'll respond Sunday from his session. If he says he has no discomfort when he reports to the ballpark, then the wheels start in motion.

"Possibly he'll have a rehab start five days from now," manager Bob Geren said. "He'll be on his regular cycle, day off, stretch, throwing, light bullpen. Nothing is written in stone yet."

Geren did say that Harden would need at least a couple rehab starts to build up his arm and make sure his shoulder is strong.

Could it mean that Harden might be back with the A's by mid-May?

"We don't want to get ahead of ourselves," Geren said.

Geren watched Harden's effort and liked what he saw.

"He threw 50 pitches, maybe two hits, one a jack, one walk and a lot of strikeouts," he said. "It's hard to count the strikeouts because we start at different counts.

"He threw the ball well. The velocity was there. It was a very positive day all the way around."

One of the participants in the simulated game was third baseman Eric Chavez, who also is on the DL with back problems. He has been cleared to swing and, in fact, got one of the two hits.

One player returned from the disabled list, pitcher Justin Duchscherer. He had been on the DL since April 5 with a strained right biceps. He started Saturday against the Mariners.

To make room on the roster, the A's optioned long reliever Lenny DiNardo (1-1, 10.57 ERA) to Triple-A Sacramento. DiNardo was 1-1 with a 10.57 ERA in four appearances, two starts. He gave up 15 hits and nine runs in 7 2/3 innings. Opponents had a .395 average against him.

"Lenny will start down there on Wednesday." Geren said. "We want to keep him stretched out and sharp."

Dallas Braden now will move into the long relief role.

The A's matched the club record last season with 22 players on the disabled list, and those players missed a record 1,259 combined games. The A's have used the DL seven times already this season and have had at least three on the DL every day.