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Danny Jackson, trying to return from a torn groin, has suffered a setback and will miss his scheduled start Saturday night.

”He felt a little tightness there about three days ago, and the trainers decided they would back him off just to be cautious,” General Manager Jim Frey said. ”How long will it be? We don`t know.”

Jackson has been disabled since April 19. He has a 5.06 earned-run average and is still looking for his first victory as a Cub. He lost his only decision.

The Cubs have replaced him with Mike Bielecki, who is 5-2 with a 3.73 ERA. It will be Bielecki`s first start since May 11. As a starter, he got his last victory April 30 and is 3-1 with a 3.69 ERA.

Still learning: After enjoying his first decent sleep in two days, manager Jim Essian spent his second day at the helm familiarizing himself with a team he only has been able to watch sporadically on television.

Essian met with Shawon Dunston behind closed doors Thursday afternoon. He said it was only one of the meetings he plans to have with players.

”I`m just trying to meet with each of the guys to talk about any concerns or problems they might have,” he said.