Sean O'Brien and Jared Payne are late doubts for Ireland's final autumn Test against Australia in Dublin on Saturday (5.30pm, live on RTÉ Radio 1 and RTÉ2).

Ireland have drafted in Munster flanker Peter O'Mahony to cover O'Brien and already had Rory Scannell on hand to cover centre Payne.

Ireland's assistant coach Andy Farrell has insisted both men had merely carried "lower-limb tweaks", and so sat out Friday's captain's run training session.

Farrell remains confident the influential duo will be fit for the Test, but Ireland will check on both men on the morning of the match.

"We've had a couple of guys that's had a couple of niggles, and the captain's run is normally just a stretching-legs type session," said Farrell.

"We made a couple of decisions this morning to rest Jared Payne and Sean O'Brien and see how they are in the morning.

"We'll have a discussion in the morning about their situation.

"They both have just lower-limb tweaks, that's what normally happens during the week.

"You pick things up on the way from the game, through the week and so on.

"The main session was yesterday and we decided to give a couple of players more time.

"We've kept Peter O'Mahony here, and we've got Rory Scannell as well covering for Jared Payne.

"All the main work's been done already, that's why we are resting them, to give them every chance to feel 100%."

O'Brien has endured a prolonged spell on the sidelines this year and missed Ireland's historic win over New Zealand in Chicago, but returned to the side that defeated Canada and retained his place for last weekend's reversal against the All Blacks.

However O'Mahony has only featured once in the autumn series, in the facile win over Canada, and it would be expected he would take a place on the bench if O'Brien is unavailable, with Josh van der Flier slotting into the starting XV.

Ireland must already face an experienced Wallabies line-up without the regular inside-backs combination of Johnny Sexton and Robbie Henshaw.

British and Irish Lions fly-half Sexton misses out with a hamstring problem suffered in last weekend's 21-9 defeat to New Zealand.

Powerful centre Henshaw suffered concussion in the Dublin loss to the All Blacks, leaving Garry Ringrose slotting in for his first-ever senior level start at number 12.

Munster's 22-year-old utility back Scannell will now offer cover for Ulster's Payne - the man who captains Ireland's back line defence.

Payne remains vital to Ireland's defensive system and shape, and Ireland will be desperate for the 31-year-old to come through, especially with the inexperienced Ringrose coming into the side.

Farrell however has insisted the late doubts have not caused Ireland any real disruption.

When asked if the fitness doubts over O'Brien and Payne had affected preparations, Farrell said: "No it hasn't, because this is what we've been building for the last year.

"We've been building strength in numbers, strength in depth is getting bigger and better all the time.

"We've seen that across the last year and on the South Africa tour and we're seeing it again."