Former world heavyweight champion Andy Ruiz Jr survived an early knockdown to beat Chris Arreola by unanimous decision in California.

Knocked down by an overhand right in the second round, Mexican Ruiz recovered to win 117-110, 118-109 and 118-109 on the judges' scorecards.

He had not fought since his December 2019 rematch defeat by Anthony Joshua, after which he lost 55lb.

"We did what we had to do to get the victory," Ruiz, 31, said.

Ruiz looked sharp with the jab in the first round before American Arreola sent him to the canvas with a shot to the temple in the second.

Ruiz was hurt again in the third when 40-year-old Arreola landed a left hook, but looked more comfortable over the ensuing rounds.

He found his rhythm with the jab in the eighth round and twice forced Arreola to shake out his shoulder - the latter occasion in the 11th with a sharp right-left combo - before staving off Arreola's desperate attempts in the final round.

"I respect the judges, but today I always said beauty is in the eye of the beholder," Arreola said.

"Honestly, man, did he win? Fine. But don't tell me you're only going to give me two, three rounds."

Ruiz now holds a record of 34 wins from 36 fights, while Arreola has lost seven of his 48 contests.

Brawls broke out in the stands during the early rounds of the fight, which took place in front of 3,940 fans at a reduced capacity Dignity Health Sports Park in Carson.