By Keith Idec

Amir Khan-Billy Dib was every bit the mismatch most expected.

Khan knocked down Dib once apiece in the second and fourth rounds, and stopped the lightweight in the fourth round of their scheduled 12-round welterweight bout Friday night at King Abdullah Sports City in Jeddah, Saudi Arabia. A left hook by Khan floored Dib about 50 seconds into the fourth round, which led to Dib’s corner men throwing in the towel.

A straight right hand by Khan started the trouble at 2:15 of the fourth round. Khan then landed a right to the body and finished off Dib with a left hook up top.

Dib attempted to get up from his gloves and knees, but referee Ian John Lewis halted the action because Dib’s handlers threw in the towel.

England’s Khan, 32, improved to 34-5 and produced his 21st knockout. The 33-year-old Dib (45-6, 26 KOs, 2 NC) lost by knockout for the third time in his 14-year pro career.

The WBC somehow sanctioned the Khan-Dib bout for its international welterweight title, despite that Khan was stopped in his previous fight and Dib had never before boxed above the lightweight limit.

Khan returned to the ring Friday night less than three months after Terence Crawford beat him by sixth-round technical knockout. Crawford won that fight for his WBO welterweight title when Khan couldn’t continue once Crawford hit him with what was ruled an accidental low blow in the sixth round April 20 at Madison Square Garden in New York.

The 33-year-old Dib moved up two weight classes – from lightweight to welterweight – to fight Khan on short notice. The former IBF 130-pound champion accepted their fight right after Khan’s original opponent, India’s Neeraj Goyat (11-3-2, 2 KOs), suffered head, face and arm injuries in a car accident June 25 and withdrew from the bout.

In his previous appearance, Dib defeated Thailand’s Surachet Tongmala (7-12, 4 KOs) by first-round knockout in a lightweight bout April 26 in Hurstville, Australia.

In the round before their one-sided bout ended, Khan continued opening up on Dib early in the third round. A left hook by Khan backed Dib into the ropes just before the halfway point of the third round.

A left hook by Khan knocked down Dib less than a minute into the second round. Dib got up and tried to keep away from the bigger fighter for most of the remainder of the round.

A right hand by Khan knocked Dib into the ropes later in the second round.

Khan landed a left-right combination in the first round, but those three minutes mostly lacked action. Dib tried to stay away.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.