Martinez was able to survive a furious final round of left hands from Chavez that knocked Martinez down. It was still a unanimous decision for Martinez, who dominated most of the fight. The result represents the first professional loss for Chavez.
"Julio fought a great fight," Martinez said. "He showed he had heart right until the end."
Prior to the knockdown, Martinez was clearly the better fighter round-to-round, as the Argentine showcased his tremendous skill and timing. Whenever Chavez would attack, Martinez found a way to switch the momentum.
The 37-year-old had previously struggled to find opponents who can challenge him, but received that challenge in the final round.
Round 12 will be remembered as the round that showed Martinez's vulnerability. Chavez nearly upset the star boxer with his aggressive assault.
Chavez called for a rematch.
"I was 20 seconds away from knocking him out," Chavez said.