CHICAGO -- Third baseman Chris Johnson is back in the clubhouse, but not in the starting lineup, after experiencing flu-like symptoms that forced him out of Friday's 8-3 win in the sixth inning.

"He walked in when I walked out," said Astros manager Brad Mills. "We tried to keep him away from being around guys and so forth, but he was pretty sick last night."

Illnesses seem to be spreading around the Astros' clubhouse. Center fielder Jordan Schafer is also out of the starting lineup against southpaw Chris Sale, and is still not feeling 100 percent, according to Mills.

"He's still got some sick symptoms and so forth," Mills said. "But for the most part he's been getting a little bit better."

Reliever Rodriguez stellar at working out of jams

CHICAGO -- Fernando Rodriguez is perfect this season when entering the game with runners on base.

The reliever has stranded all 15 of his inherited runners this season, a feat he focused on achieving before the season began.

"It started from Spring Training when they ask you what are your goals for this year," Rodriguez said. "That was my number one goal. That's something I really wanted to accomplish."

Rodriguez said the starters have taken notice, coming to him after the game to thank him. He said he thrives in situations with runners on base, and knows the starters are protective of their ERAs.

"It's kind of funny," Rodriguez said. "I've been thinking about it. I do a pretty good job coming in during the inning like that. But when I put a few runners on, sometimes it ends up finding that little hole and the runs come in."

Astros manager Brad Mills said Rodriguez and Wilton Lopez are relievers he can trust to get starters out of jams.

"Nobody wants to come out with their runners on base, especially with the bases loaded," Mills said. "Sometimes, with pitch count or how they're pitching or whatever, almost dictates that. To have these guys come in and take that responsibility upon themselves to get out of the inning is huge."

Martinez to seven-day DL; Downs recalled

CHICAGO -- Matt Downs returned to the Astros from Triple-A Oklahoma City, while outfielder Fernando Martinez went on the seven-day disabled list with concussion-like symptoms.

"He came in after the game on Wednesday and said he was having blurred vision and wasn't feeling really well," said Astros manager Brad Mills. "As they talked about it a little bit more, they said it sounds like a concussion-type thing."

Martinez told Mills he had been hit in the head with a pitch at Oklahoma City on May 26, a couple days before being called up to the Astros.

Mills said Martinez's tests came back negative after the game, but a diving play on Wednesday may have triggered post-concussion symptoms. He said Martinez saw team doctors on Friday, and they ordered future tests that can't happen until Monday.

"We're going to be into this thing four or five days before we even get any results," Mills said. "The first doctor he saw said it sure sounds like a concussion syndrome. We weren't going to be able to play him or use him, so we needed to get somebody here."

Downs, who was with the Astros at the beginning of June, rejoined the club from Oklahoma City, providing Houston with another utility player. Brian Bixler, another athlete who can play across the diamond, joined the Astros on Friday when Marwin Gonzalez went on the disabled list. Both Downs and Bixler were in the starting lineup on Saturday.

"Last night they called me after the game," Downs said. "They said they didn't know what was going on, but I was going back up. Kind of a short stay down there."