Ulises Solis successfully defended his IBF light flyweight title when Will Grigsby failed to answer the bell before the ninth round in Las Vegas.
The 25-year-old Mexican (23-1-2) dominated the first eight rounds of their rematch without any knockdowns.
His 36-year-old American opponent (18-4-1) then stayed on his stool with four rounds of the fight remaining.
Solis, who weighed in at 108lbs (49kg), won the title a year ago with a unanimous decision over Grigsby.