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Pitching coach Billy Connors has right-hander Frank Castillo cutting back the work he does between starts to make sure he can finish the season healthy. Castillo (7-10) is scheduled to start Saturday at Wrigley Field against Dave Burba (2-6) and the San Francisco Giants.

Castillo already has 156 2/3 innings, 20 more than he threw all last season with the Cubs and Triple-A Iowa combined. The most Castillo has pitched in six professional seasons was 1989, when he combined for 197 1/3 innings at Double-A Charlotte and Class-A Winston-Salem.

”It`s a lot different throwing in the big leagues,” says Connors, who is keeping a close eye to make sure Castillo doesn`t over-extend himself.

”I`m backing him off on throwing between starts and some of the other workouts. He works so hard. You have to keep holding him back.”

– The Cubs are hedging their bets with injured pitchers Mike Harkey and Shawn Boskie. Harkey is scheduled to start Tuesday against the Dodgers. Harkey strained a groin muscle Aug. 20 in a win against the Giants at San Francisco and missed his next scheduled start Tuesday when he aggravated the injury during warmups. The last-minute scratch caused problems for the Cubs, who had to scramble to find a starter. They were forced to use all-purpose pitcher Jeff Robinson, who had worked in relief the night before. In case Harkey has to take himself out at the last minute Tuesday, the Cubs are maneuvering things so Boskie will be ready. Boskie has been on the disabled list since July 27 with a sore muscle under his collarbone. He is on rehabilitation assignment in the minor leagues, where he pitched well last Tuesday. He will work a couple innings Saturday and then be brought to Chicago Tuesday to back up Harkey.

– Tuesday, major-league rosters can be expanded to 40. The Cubs won`t have to send anybody down when they bring Boskie up. But General Manager Larry Himes says Boskie will be the only pitcher brought up to the big club and could be the only player, period. ”There`s not much help for us down there right now,” says Himes. One name that comes to mind is Fernando Ramsey, probably the best defensive outfielder in the Cubs` minor-league system and a speedster who once ran track for the Panamanian Olympic team.

– Shortstop Shawon Dunston will see the team doctors Saturday for his latest checkup. Dunston, who had back surgery in May, has been taking ground balls at short. But he has yet to swing a bat.