CHICAGO -- Giants manager Bruce Bochy said right-hander Merkin Valdez, at the probable expense of Bob Howry, would get a chance as a setup man for closer Brian Wilson.

Before the Giants extended their lead in the eighth inning of Tuesday's victory against the Cubs, Bochy sent Valdez to warm up in the bullpen. Without the extra runs, Valdez would have been protecting a one-run lead for starter Tim Lincecum.

The eighth is often Howry's territory, but he is 0-2 with a pair of blown saves and a 4.35 ERA. Left-handers are batting .400 against him and righties are doing OK at .281.

"I did talk to Bobby," Bochy said. "He got derailed there a little bit. I said, 'Listen, I'm going to mix in Valdez late in ballgames.'"

Howry, who signed as a free agent in the offseason, has a history of slow starts; he has said that his fastball is missing a few miles per hour in the first month of the season. Bochy does not look at the move as a demotion for anyone, just a spreading of the opportunities.

Valdez allowed a shallow single and a walk in the eighth, but struck out two.

"Merkin, I like the way he threw," Bochy said. "Looks like he's getting more and more confident with it. It's nice to have a guy in the mix that throws 96 [mph]."

Bochy said that another right-hander, Brandon Medders, also could get a late call against righties. When a left-hander is required, Jeremy Affeldt would continue to be used, Bochy said.