The Australian Rugby Union says it is surprised and disappointed that the IRB is to appeal the decision to clear James Horwill of stamping during the first Test against the Lions.

Replays showed the Aussie captain bringing his right boot down onto the head of Alun-Wyn Jones, who was lying at the bottom of a ruck.

Horwill was cited, but then cleared of stamping by the ARU.

Meanwhile, Lions head coach Warren Gatland said Sean O'Brien and Conor Murray will have an impact off the bench against the Wallabies in Saturday's second Test in Melbourne.

Dan Lydiate has replaced Tom Croft in the back row while Ben Youngs has taken over from Mike Philips who drops out of the match-day squad.

©INPHO/Billy Stickland