ALAMEDA, Calif. (AP) Star receiver Antonio Brown returned to training camp with the Oakland Raiders on Monday, a day after being given an ultimatum by general manager Mike Mayock to be "all in or all out."

Brown took part in meetings in Napa before the team broke camp, a person familiar with the situation said on condition of anonymity because the team didn't release details.

Brown didn't attend practice Sunday as he works to find a helmet that he's comfortable using and that meets safety standards set by the NFL and NFLPA. Brown lost a grievance last week seeking to use the Schutt Air Advantage helmet he has used throughout his career because it was too old to be certified as safe.