PRO FOOTBALL / DAILY REPORT : NFC : Young Leaves 49er Practice Field Early

San Francisco 49er quarterback Steve Young, who has sat out three games because of a bruised left shoulder, left practice early Thursday because of continued pain. Backup Elvis Grbac, who had sprained his left ankle, was upgraded from questionable to probable for Sunday’s game against Dallas at Irving, Tex.

San Francisco Coach George Seifert said the team will decide Saturday or Sunday whether Young will play.

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Even with an extra three weeks, there’s so much to do to get the $280-million Trans World Dome ready for Sunday that the St. Louis Rams can’t practice there this week. The artificial turf field looked ready with a giant Ram helmet at the 50-yard line, but the goal posts were getting coats of paint and one base hadn’t been padded yet. . . . The Rams activated offensive tackle Jackie Slater and released defensive back John Reece. Slater, 41, will play in his 20th season and 259th game Sunday. He’s coming off off-season surgery on his left elbow.