Former 49ers quarterback and frequent concussion sufferer Steve Young, evidently concerned over performing well in a December 1995 game against the Buffalo Bills, has sequestered himself in his office to study game film for the matchup, Young's tearful wife, Barbara, said yesterday. 'He'd been moody and anxious for a couple days, but I didn't worry until he turned to me and said, 'Big game this week,'' a visibly shaken Mrs. Young told reporters, adding that she was afraid to call the neurologist for fear of what he might find. 'Steve said, 'I'm going to go take another look at the tapes and see if I can find the holes in the Bills coverage. I won't let you down, Coach Seifert.' Then he kissed me tenderly and shuffled off.' Since the episode, Young has been seen muttering to himself, diagramming plays, and scrawling copious notes while watching a Law & Order rerun marathon. 