GLENDALE, Ariz. (AP) – IBF junior welterweight champion Kostya Tszyu retained his title Saturday night, demolishing Sharmba Mitchell in less than three rounds of the long-awaited rematch between the former titleholders.

Tszyu (31-1) knocked Mitchell down four times – three in the third round.

The last time, the relentless native of a Russian steel-mill city dropped Mitchell to his knees with two combinations, then hit him with two right hands, two lefts and a right before referee Raul Caiz stepped in at the 2:48 mark.

Tszyu was credited with a seven-round technical knockout of Mitchell (55-4) when they fought on Feb. 3, 2001. But that was because Mitchell had to retire after reinjuring his left knee. This time, Tszyu, a former champion of all three major divisions, left no question about his supremacy at 140 pounds, getting his 25th knockout and improving to 15-1 in world championship bouts.

In non-title bouts involving prominent boxers, WBO super bantamweight champion Joan Guzman won a 10-round unanimous decision over Joe Morales of San Antonio, and former junior middleweight champion Yory Boy Campas beat an eight-round decision over Raul Munoz of Mexico.

The main event of a 10-round card was years in the making.

Tszyu, who held the WBC crown, took Mitchell’s WBA title in their first match. Then Mitchell had surgery and was out of the ring for 13 months.

In the meantime, Tszyu went on to unify the weight class by knocking out Zab Judah for the IBF belt three years ago before running into his own set of medical problems.

While Mitchell went on an eight-bout winning streak, Tszyu defended his triple crowns just twice – the last time against James Leija on Jan. 19, 2003. But Tszyu tore an Achilles’ tendon eight months later – just before his scheduled rematch with Mitchell in Moscow – and then tore a shoulder tendon in January training for Mitchell again.

Tszyu’s inactivity cost him the WBC and WBA titles.

The IBF gave him a medical exemption, but after the shoulder injury, it also set up an interim title bout between Mitchell and Lovemore N’Dou on Feb. 7. Mitchell won a unanimous decision and would have become the IBF champion if Tszyu hadn’t fought him.

Tszyu hastened the retirement of six-time world champion Julio Cesar Chavez by knocking Chavez out in Phoenix in July 2000. Over four years later, Tszyu was roundly booed at the start of this bout.

But the crowd came around to cheer him for his artistry.

Tszyu, traditionally a slow starter, showed no rust after nearly two years away. Enraged by a head butt that bloodied his nose in the first round, the 35-year-old Tszyu backed Mitchell into the ropes and hit him with a hard right that dropped him to all fours late in the second.

The third had barely begun when Tszyu put Mitchell, 34, on his back with a straight right. The next knockdown, he drove Mitchell into the ropes with combinations, foreshadowing the decisive fourth trip to the canvas for the challenger.

On Friday, Guzman (22-0) scuttled his title defense against Marcos Licona of Mexico City by weighing in at 1281/2 pounds – 61/2 over the limit – and Licona pulled out.

Morales (18-7) took what turned into a featherweight bout and looked like a substitute early, taking a beating in the fifth round when Guzman punished him on the ropes. He fared better after that, but never got close to the knockout he needed to pull an upset.

Campas (85-6), a popular Mexican fighter who lives in Phoenix, earned his fifth victory since Oscar De La Hoya stopped him in the seventh round of their WBC 154-pound title match in May 2003. Campas knocked Munoz (15-5) down once.

AP-ES-11-06-04 2211EST