The sidewinder who baffled hitters at the Phillies' camp in Clearwater, Fla., last week seemed washed up two years ago. Sean Fesh blew out his left elbow while in the Padres' system in 1995. After reconstructive surgery he hung around the minors until he was let go by the Mets in '97. But Fesh wouldn't quit. He phoned every big league organization, offering to fly anywhere at his own expense for a tryout. He had switched to a sidearm delivery, he said, and gained velocity and movement. The clubs' response: a collective yawn. Last May at a Triple A game in Scranton, Pa., Fesh spotted Phillies senior adviser Dallas Green in the crowd and pestered him for a tryout. Green amazed him by promising to arrange one. The next week the Phils signed Fesh to a minor league deal. He saved nine games for Double A Reading in '98, striking out 41 in 33 innings with a 1.36 ERA. This year he'll probably be the closer for Scranton/ Wilkes-Barre, the Phillies' Triple A affiliate. Sitting by his locker last week, the 26-year-old Fesh wore a big league uniform and a big grin. "I won't stop playing this game until they rip this jersey off me," he said.