The move means the team's Opening Day starter won't be eligible for the postseason should Los Angeles qualify.
The switch-hitting Furcal got off to a great start this season, hitting .366 in 32 games before being placed on the disabled list May 6 because of back problems. He hasn't played since, having undergone surgery July 3 to relieve pressure on a disk in his lower back.
"In the right situation, we'll look to get him in the field," Dodgers manager Joe Torre said.
Penny, a 16-game winner each of the past two seasons, was 6-9 with a 6.27 ERA in 19 games -- 17 of them starts. He's been bothered by shoulder problems most of the season.