Andy Farrell says he isn't worried by the sloppy nature of Saturday's 35-17 win against Fiji, but says his side need to be wary of "false dawns" in the future.

Saturday's performance was several gears below the win against the world champions, and while Ireland never looked like losing against Vern Cotter's side, they made heavy work of putting the game to bed, having spent 25 minutes playing against 14 men, and a further 10 minutes with a two-man advantage, after Fiji picked up both a red and yellow card in the second half.

Continuity of performance was always likely to be a challenge for Ireland on Saturday, with Farrell having made nine changes from the win against South Africa, while Robbie Henshaw also departed in the opening minutes due to a hamstring injury.

But with Farrell having stressed the need for his wider squad to step up to the mark in recent weeks, he didn't hide his frustration in the immediate aftermath of the game.

And he says it's vital those stepping into the team bring the same levels of leadership.

"I'm not worried, there’s a lot of big characters that weren’t in the changing room.

"I’m big on how you make people feel, or how certain people make people feel. We had different leadership going on this week in all sorts of areas. It's something we need to get to the bottom of and keep progressing with.

"Sometimes you get a performance and it leads you into a false dawn. It’s good, especially off the back of a win, to really get into the bones of it and have a good dig down deep and see what the reality is."

Tadhg Furlong captained Ireland in absence of Johnny Sexton

The obvious, and concerning, coincidence was the drop-off in performance without Johnny Sexton, who suffered a dead leg in the win versus South Africa.

His replacement, Joey Carbery, had been performing reasonably well in his absence, before being replaced early in the second half following the dangerous tackle by Albert Tuisue which saw the Fijian red-carded.

And although Jack Crowley produced some impressive flashes in his 35-minute cameo, Sexton's absence looked to be an issue.

However, Farrell says it's an important learning curve for the fringe players to find out the challenges of Test rugby the hard way.

"It's not just Johnny, look at the experience that’s out of the side and it’s not just the injured lads - Bundee [Aki], Iain Henderson, Keith Earls not being here.

"Certain people understand their role and fit in the side, and they’re able to be themselves and go after that because they’re comfortable in their own skin. When you’re missing so much, then people know they will need to try and fill that vaccuum.

"But they need the experience of being able to do that at the same time. At least we know where we’re at."

One area Ireland don't look understaffed is the back row.

Josh van der Flier should be a leading contender for World Player of the Year in the coming weeks, but in spite of his absence, Ulster's Nick Timoney slotted in seamlessly, and was Ireland's best performer, scoring two of their five tries.

Likewise, Leinster's Max Deegan (below) came off the bench in the final 20 minutes for a long-awaited second cap, nearly three years on from his debut, and Farrell says he made a big impression in the final quarter.

"He [Deegan] was unlucky not to go on the tour [of New Zealand] because he played really well at the end of last season.

"He has started the season really well. He was really good for Emerging Ireland and deserved his shot today. He came on and carried strong, got over the gainline.

"At times today I felt our breakdown work flattered to deceive in the sense they weren’t putting bodies away quick enough. A lot of that was down to our carrying, which at times was inconsistent, but when Max came on he got us over the gainline. It becomes a little bit easier."

Ireland finish their Bank of Ireland Nations Series on Saturday when Australia visit the Aviva Stadium, with Dave Rennie's side coming off the back of a shock defeat to Italy in Florence.

Farrell says it's too early to tell how many of his frontline players will be fit to return against the Wallabies, but did confirm the Iain Henderson and Bundee Aki will be available, the latter returning from his seven-week suspension following a red card in the URC in September.

And the Irish coach says he expects a big backlash from the two-time world champions.

"You look at their side, I know they made plenty of changes, probably because they’re looking at us this week. It will certainly focus the mind.

"We know what’s coming, given their performance with probably a similar side that’s going to be put out against us in Paris last week. They were very strong, especially set-piece wise. They went after the French and nearly got the big 'W' over there. That’s the type of game we’re expecting."

Follow a live blog of Ireland v Australia on RTÉ.ie/sport and RTÉ News app this Saturday from 8pm with live radio commentary on RTÉ Radio 1.