NEW YORK -- Any ring rust on Arturo Gatti from a 10-month layoff must have fallen off on his way to work Saturday night.

Gatti, a former IBF junior lightweight champion, knocked down Terronn Millett, a former IBF junior welterweight champion, three times and stopped him at 2:23 of the fourth round.

The scheduled 10-round bout preceded Shane Mosley's WBC welterweight title challenge against Vernon Forrest before a sellout crowd of 5,000 fans in the Theater at Madison Square Garden.

Gatti, whose left eye was almost closed, scored the first knockdown with a right to the head with about 35 seconds left in the third round. Millett struggled up at the count of six, then withstood a barrage and almost went down again from a left-right just before the bell.

Gatti, who weighed 141½, knocked down Millett, 142, with another right hand at 1:55 of the fourth round. This time Millett struggled up at the count of four. Gatti leaped to the attack, and a four-punch combination dropped Millett again.

Referee Jim Santa then halted the fight without a count.

It was an impressive win for Gatti, who had not fought since he was stopped by Oscar De La Hoya last March 24.

"I felt great tonight," Gatti said. "I got tired in the first round, but Buddy (new trainer Buddy McGirt) told me to keep my composure. I learned to stay calm tonight."

The 29-year-old Gatti of Jersey City, N.J., a junior lightweight (130 pounds) champion in 1995-97, now has a 34-5 record with 28 knockouts.

Millett, 32, of St. Louis, held his own in an action-packed second round before Gatti took complete charge in the third. The IBF junior welterweight (140 pounds) champion from 1999-2000 fell to 26-3-1 with 19 knockouts.