One of George Kambosos Jr.’s stablemates pulled off an upset on his undercard Saturday night in Shawnee, Oklahoma.

Australian heavyweight Joe Goodall dropped Stephan Shaw twice during the sixth round and won their bout by technical knockout on the Kambosos-Maxi Hughes undercard at FireLake Arena. Shaw got up from both knockdowns, but his trainers instructed an Oklahoma State Athletic Commission official to have referee Gary Ritter stop their scheduled eight-rounder with five seconds to go in the sixth round.

The official time of the stoppage was 2:55 of round number six.

Brisbane’s Goodall improved to 10-1 and produced his ninth knockout. St. Louis’ Shaw (18-2, 13 KOs, 1 NC) lost a second straight bout.

Shaw, who went down for the first time in his career Saturday night, fought for the first time since hard-hitting Nigerian heavyweight Efe Ajagba beat him by unanimous decision in their 10-rounder January 14 at Turning Stone Resort Casino in Verona, New York.

On Saturday night, a three-punch combination by Goodall, which was punctuated by a left hook, knocked Shaw flat on his back with 1:11 to go in the sixth round. Shaw barely answered Ritter’s count in time, but he didn’t remain on his feet for long.

Another three-punch combination – this time a left-right-left – knocked Shaw to the canvas again with 51 seconds to go in the sixth round. Ritter nearly counted to 10 again, but Shaw was able to beat the count and fought on.

Goodall continued to hit Goodall with big power punches until Shaw’s corner men threw in the towel late in the sixth round.

Goodall previously landed a right uppercut and then an overhand right barely a minute into the sixth round.

A clean right by Shaw landed with about 15 seconds to go in an action-packed fifth round. A sweeping right hand by Goodall connected with just over 1:05 on the clock in the fifth round.

A right-left combination by Goodall landed just before the halfway point of the fifth round. Goodall’s right caught Shaw with 2:10 to go in the fifth round.

Goodall clipped Shaw with a left hook when there were just over 10 seconds remaining in the fourth round. Ritter warned Goodall with 1:45 to go in the fourth round for hitting Shaw behind his head.

Shaw’s left hook knocked Goodall off balance in an exchange a few seconds before the third round concluded.

A left-right combination by Goodall connected with just over 30 seconds on the clock in the third round. Shaw’s right to the body was effective a few seconds after the midway mark of the third round.

Goodall drilled Shaw with a right hand that initiated an entertaining exchange in the final 10 seconds of the second round. Goodall landed a right hand that got Shaw’s attention at exactly the halfway point of the second round.

Shaw landed several right hands to Goodall’s body during the first round. Goodall split Shaw’s guard with a left uppercut with just over a minute to go in the opening round.

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