Pittsburgh also received help from a new face in right-handed starter Yoslan Herrera, a Cuban defector the Pirates signed to a Major League contract in 2006.
Osoria is coming back from a five-day stint with the Indians, where he went 1-0 with three scoreless innings of work and three strikeouts. The Pirates placed Osoria on the disabled list on June 28 because a right ankle injury affected his delivery and hampered the control of his sinker.
"The ball wasn't sinking as much," manager John Russell said. "It's basically his bread and butter. Things like that happen. You start to try to throw a little different. I think his arm got tired. He didn't have life on the ball like he used to. Certain things started to happen as far as with the foot and things. It can very much affect the pitching mechanics."
The Pirates' skipper said he'll use Osoria without hesitation on Saturday night against the Cardinals. Osoria was 3-2 with a 6.02 ERA in 36 appearances before his injury.
"I think this a great opportunity for him, not only to get healthy, but to get his arm strength back," Russell said.
As for Herrera, this is the 27-year-old's biggest opportunity since coming to the United States from Cuba in July 2005. Herrera has pitched for Double-A Altoona for parts of the last two seasons.
He posted a 6-9 record and 4.69 ERA in 2007 and has improved to 5-8 with a 3.11 ERA this season.
"We haven't seen much of him," Russell said. "He's throwing the ball very well from what I understand. He's a strike thrower, but has some different pitches. He's not necessarily a power pitcher, but a guy who knows how to pitch a little bit.
"We're looking for somebody to come up and throw strikes, keep the ball down and give us a chance to win. From all the indications that we've heard, Yoslan is the kind of guy will give that start to us."
The Pirates don't know if Herrera has the physical or mental capabilities to become an everyday Major League starter. Saturday night will be the first indication.
"This is not a one-night find-out either," Russell said. "We like him. One outing is not going to make or break. It would be nice to see a nice outing."
Todd Krise is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.