MESA, Ariz. -- The Cubs trimmed eight players from the spring camp roster, including 2008 No. 1 Draft pick Andrew Cashner.

Cashner, who was on the travel squad and expected to pitch on Friday against the Chicago White Sox, had appeared in three games and given up one run on four hits and five walks over five innings.

"There's no reason why this young man can't have an impact on our team this summer with the stuff that he's got," Cubs manager Lou Piniella said on Friday. "He's worked hard, he's made some improvement, and he should go down there and dominate."

Cashner needs more experience, Piniella said, and will start in the Minor Leagues.

"As a starter, you get a chance to throw more pitches, you get a chance to be out there a longer period of time and work on things," Piniella said. "He's got a nice arm and a great future ahead of him. He's just got to improve a little."

Pitchers Blake Parker and Jeff Stevens and catcher Welington Castillo were optioned to Triple-A Iowa. Stevens, acquired from Cleveland in the Mark DeRosa deal, appeared in 11 games with the big league team last year and posted a 7.11 ERA. This spring, the right-hander had four innings over four games and had given up eight runs (four earned) on five hits and three walks.

"He's working on a slider now, and I think that will be a real nice complement to his fastball," Piniella said. "The curve he throws is a different plane pitch and not only that but umpires don't call it as often. Getting a smaller break on his slider will help."

Cashner was one of five non-roster invitees assigned to the Minor League camp. Others include pitchers Casey Coleman, Thomas Diamond and J.R. Mathes and infielder Bryan LaHair.

"Coleman's an interesting young guy," Piniella said of the right-hander. "He's got all the pitches. I think facing experienced hitters in Triple-A will help him. He's a kid you can project as a rotation pitcher in the future."

Coleman also was scheduled to pitch on Friday. Piniella gave him and a couple of the others the message that they shouldn't worry about being sent down.

"[I said], 'When you come back, stay here and do well,'" Piniella said.

Diamond was a non-roster invitee who was claimed off waivers from Texas, and had not given up a run in 4 1/3 innings. The right-hander needs to work on his breaking pitches, Piniella said. He gave up one hit and three walks in three games.

The roster is now at 42, including 18 pitchers, four catchers, 12 infielders, and eight outfielders.