Joey Bosa handled his business at Chargers Park for the past month, attending nearly every team function and improving over the course of organized team activities. But his spring has come to a sudden, apparent end. It's business. The Chargers began their three-day minicamp Tuesday morning without their No. 3 overall pick, a source said. Attendance is mandatory for all players under contract, and there is the rub. Bosa's camp has advised him to hold out amid a stalemate in negotiations. The former Ohio State defensive end skipped last Thursday's final OTA practice for the same reason, sources said. His absence at the voluntary session, which was closed to reporters, gave the Chargers indication he might miss Tuesday, too. This situation is rather unusual. Bosa is the last of the top 19 selections in April's draft to be unsigned. All of the Chargers' draft picks last year were signed before the team's May rookie minicamp.