LAS VEGAS – Eduardo Ramirez left no doubt about his rematch with Leduan Barthelemy.

The aggressive, determined Mexican dropped Barthelemy with a right-left combination in the fourth round of their 10-round rematch Saturday night at MGM Grand Garden Arena. The featherweight contender got full extension on his straight left hand, which sent Barthelemy stumbling backward and to the canvas.

Barthelemy answered referee Russell Mora’s count in time. Once he turned his back on Mora and Ramirez, Mora stopped their fight with one second remaining in the fourth round on the Deontay Wilder-Luis Ortiz undercard.

Ramirez improved to 23-2-3 and produced his 10th knockout. The Cuban-born, Las Vegas-based Barthelemy lost for the first time as a pro (15-1-1, 7 KOs).

Barthelemy and Ramirez fought to a 10-round split draw in September 2017 at Cannery Hotel & Casino in Las Vegas. Ramirez maintains he did more than enough to win that bout, thus he made sure not to allow the judges to determine this outcome.

Ramirez blasted Barthelemy with multiple hard, left hands in the second half of the fourth round. Those shots wore down Barthelemy and enabled Ramirez to press forward and land the combination that ended their fight.

Ramirez connected with several power punches just after the midway mark of the third round. Later in the third, Ramirez hit Barthelemy with a right hook, yet he didn’t quite catch him flush with that shot.

The Barthelemy-Ramirez match was the first of four fights FOX Sports aired as part of its Wilder-Ortiz pay-per-view show. Bantamweights Luis Nery (30-0, 24 KOs) and Emmanuel Rodriguez (19-1, 12 KOs) were supposed to square off in the first pay-per-view bout, but Rodriguez refused to fight after Nery came in one pound over the bantamweight limit of 118 pounds at their weigh-in Friday.