WATCH: Joe Schmidt explains why he had to leave Sean O’Brien out today

*Half the Irish nation goes Googling 'hip flexor'.*

Sean O'Brien is out of Ireland's final Test match of the year. Josh van der Flier is starting at openside and Peter O'Mahony is drafted onto the bench. The news had been rumoured as early as yeasterday morning but became reality at 4:15pm this afternoon. https://twitter.com/patmccarry/status/802549369316769792 Joe Schmidt spoke with RTE just after his team hustled up to the Aviva Stadium to get ready for the Wallabies. He told them:

"It was always going to be tight. Both he and Jared Payne were looking good earlier in the week and it looked like they were going to make it. Unfortunately, Seanie didn't. "It's just a tight hip flexor. It is nothing too catastrophic but it would be an undue risk to put him out there tonight."

Schmidt said the O'Brien withdrawal was 'not ideal' when added to the loss of Johnny Sexton and Robbie Henshaw to injury.

Schmidt: O'Brien injury not ideal but too risky to play him against Australia https://t.co/Enb9LCwbej https://t.co/QmCq3g0OrV

— RTÉ Rugby (@RTErugby) November 26, 2016

"Peter O'Mahony played a stormer when he played Australia here, two years ago," Schmidt added on an optimistic note. Dick Clerkin makes his GAA Hour debut to talk about a wonderful career and argue passionately with Colm Parkinson over Sky Sports GAA. Subscribe here on iTunes.