SAN DIEGO -- Astros closer Brandon Lyon remains on course to begin a rehab stint Sunday at Triple-A Oklahoma City after throwing a simulated game Thursday at PETCO Park. Lyon has been on the disabled list since May 5 with right biceps tendinitis and a partial tear of his rotator cuff.

He threw about 20 pitches to hitters Thursday in what he described as a step in the right direction.

"I thought it went pretty good," he said. "It was my first time out there and seeing hitters. I felt better than I expected to."

Lyon threw without any hesitation and wasn't thinking about getting hitters out.

"I was trying to work on some things, get an idea of seeing a hitter up there," he said. "I had [Angel] Sanchez batting left-handed, so I didn't take it too seriously. I was just trying to work on throwing to a catcher and working on location, knowing someone isn't try to kill it. I felt good, and it was a step in the right direction."

Lyon, who blew four saves and allowed nine earned runs in 11 1/3 innings, is scheduled to pitch Sunday and Tuesday for Oklahoma City.

"I had a lot more strength in my arm and I'm bouncing back quicker day to day," he said.

Injured Wandy starting to let loose

SAN DIEGO -- Wandy Rodriguez admitted he felt a little timid at first, worried that the discomfort in his left elbow would still be there. Soon, he was throwing free and easy and was beginning to see a light at the end of the tunnel.

Rodriguez threw 35-40 pitches in the bullpen prior to Thursday's game against the Padres and said he felt fine. He's been on the disabled list since May 23 with effusion -- a fluid buildup -- in his left elbow. He'll test his arm again in the bullpen Sunday.

"I feel a lot better," he said. "Today, I didn't throw 100 percent with my breaking ball. I threw nice and easy. Sunday, I want to throw 100 percent. Sunday, [general manager] Ed Wade and the manager [Brad Mills] will know whether I'm ready or not."

Rodriguez, who's 3-3 with a 3.41 ERA in 10 starts this year, could return to the rotation when the Astros head home next week to face the St. Louis Cardinals.

"We're going to evaluate that a little bit and he how he feels [Friday] after he throws and so on," Mills said. "We'll know more [Friday]."

Downs preparing to see time in left field

SAN DIEGO -- Although outfielder Jason Bourgeois is only days away from returning from the disabled list, Matt Downs took some fly balls at PETCO Park's spacious left field prior to Thursday's game just in case he's needed at some point during the four-game series against the Padres.

Downs has never appeared in the outfield in a Major League game, but he's got extensive experience. With the Giants in 2009, he spent the entire spring playing in left field and then played half of the season there at Triple-A. He's been taking fly balls for a week and is getting more comfortable.

"We only have four [healthy] outfielders, so they told me to get out there and work in left field," Downs said.

Unlike Minute Maid Park, where it's only 315 feet down the left-field line, PETCO Park requires left fielders to cover much more ground. It's 336 feet down the line and 401 feet to the wall in the left-center power alley.

"They have a big outfield out there," Downs said. "There's a lot of room to run. That can be good and that can be bad, I don't know."

Worth noting

• Astros catcher Humberto Quintero, who's been on the disabled list since May 28 with a high ankle sprain, isn't with the team in San Diego. Quintero recently had an MRI exam and is undergoing physical therapy in Houston.

"We'd like to get him back as soon as possible, but we want to make sure he's 100 percent and doesn't come back too early," manager Brad Mills said.

• Outfielder Jason Bourgeois felt so good after getting some at-bats in extended spring training that he decided to start his Minor League rehab assignment a day earlier.

Bourgeois went 2-for-3 with a walk and two runs scored Thursday at Triple-A Oklahoma City as he tries to work his way back from a strained left oblique that's had him on the DL since May 8.