Rob Simmons will line up at lock for the Wallabies against the Pumas.
Rob Simmons will line up at lock for the Wallabies against the Pumas. Alastair Grant

Cheika picks sixth set of locks for Pumas

RUGBY: Wallabies coach Michael Cheika has tinkered with the engine room of his forward pack, this time replacing lock Kane Douglas with Rob Simmons.

Douglas is a shock omission for Saturday's Rugby Championship clash with Argentina at Perth's nib Stadium after having played all three Tests this season since his return from a knee reconstruction.

Simmons had been out of favour since the first Bledisloe Cup clash in Sydney, but now will play alongside Adam Coleman as Cheika fields his sixth locking combination of the season in seven Tests.

The three-quarter-line remains unchanged but Drew Mitchell has been dropped from the bench after struggling for fitness since returning from a groin injury, playing only 11 minutes in Brisbane in the win over the Springboks.

Henry Speight replaces Mitchell.

Rookie prop Tom Robertson and back-rower Lopeti Timani are named on an extended bench and could be in line to be the Wallabies' eighth and ninth debutants of this season.

Robertson, 22, seems likely to replace reserve tighthead Allan Alaalatoa, who is in Sydney receiving treatment on a knee injury.

Meanwhile, Argentinian flanker Juan Manuel Leguizamon, who missed last weekend's defeat by the All Blacks, said the Pumas needed to play hard for 80 minutes to avoid the Wallabies racking up second-half points as the Kiwis did.

"We need to keep the intensity during the whole game because for us it is something that we need to improve on and work on,” he said.

"Some games we play, most of the time we keep the intensity but a lot of games we don't do it and we need to improve in that.

"The breakdown will be very important for us.

"The Wallabies are good there and they have a couple of players that are very good, so we need to account for that.”