But the crowd was not impressed with the slow pace, and the fight was greeted with silence and occasional booing.
In the 11th round, though, Saunders found his form and dropped Coceres three times before the Englishman was declared the winner by TKO.
“There’s no excuse, that performance was not worthy of Canelo or any of the other big names,” Saunders said.
“I knew by round nine that I had to get him out of here. My timing wasn’t right, my head wasn’t right, nothing was right.
“I’m not one for excuses. I needed to let him gas out then attack.
“I’ve got the win and I’ve got to thank the American fans and I hope they tune in again because that wasn’t the best of me.”
In the headline fight, Britain’s KSI won his bout against fellow YouTube personality Logan Paul.
The fight at the Staples Center was won by the Watford product in a split decision, with two of the three judges siding with him.
The pair first fought last year in Manchester but a “majority draw” was declared after six rounds.
“Last time I was scared to fight,” KSI, whose real name is Olajide Olayinka Williams JJ Olatunji, said after the match.
“This time I just went in. I just kept going and going.”
“He couldn’t deal with my jabs. I got him.”