Zambrano was suspended without pay after the tantrum, and by switching to the restricted list, the Cubs can add a pitcher to the roster. Zambrano will be evaluated by doctors and given a program to follow. If all goes well, he would rejoin the Cubs after the All-Star break.
Chicago now has four rookies in the bullpen in Russell, Stevens, Andrew Cashner and Brian Schlitter.
"As an organization, I think we're a little further along with the arms we have," Cubs manager Lou Piniella said. "We bring them up and they compete and do a nice job. Actually, my young players are doing well also. Our young players aren't the reason we're not winning ballgames."
Russell began the season with the big league team and posted a 2.33 ERA in his first 17 outings with the Cubs.
"Back to work," Russell said.
The lefty, who was optioned to the Minor League team on June 12, had a 5.73 ERA in five relief outings at Iowa.
"It's a tough deal with Grabow going down -- you don't want to see that," Russell said.
At Iowa, Russell fine-tuned his pitches.
"I just worked on locating my fastball better, and I had to figure out my changeup, because it kind of left me for a while," Russell said. "Overall, I built off what I did up here."
Stevens had been sent down to Iowa on Saturday because the Cubs needed a fresh arm following Friday's game. Zambrano lasted one inning and was then sent home because of his outburst.
"I understood the move and wasn't too upset," Stevens said.
Stevens never got into a game with the Iowa Cubs this time because he spent Sunday traveling from Chicago to New Orleans, but never made it and spent that night in Miami. On Monday, he joined the Iowa Cubs in New Orleans, but that game was postponed because of rain.
"I played catch," Stevens said. "I did rack up some frequent flyer miles."
He had no record and a 2.81 ERA in 14 Major League relief appearances this season, holding batters to a .230 average.
"They said, 'Go down, and we'll get you back here as soon as we can,'" Stevens said of the message he got Saturday. "I didn't know if it would be two days, two weeks, two months."