Sportal.co.nz 22.Jun.2013Getty Images
Farrell is more qualified to speak about Folau's Test debut in the 15-man code having himself represented England in both codes.
And while the rugby league legend respects Folau's natural abilities, he has questioned the former NRL star's ability to defend on the right wing on debut against the Lions after just one Investec Super Rugby appearance in the position.
"We obviously know his qualities, he's been an outstanding player for the Broncos and Melbourne and he is some talent," Farrell said less than 24 hours after head coach Warren Gatland confirmed the Lions will target Folau in defence on Saturday night.
"He seems to find a way of getting his hands free and offloading the ball and making things happen and we heard Robbie (Deans) say that yesterday and it's true in that regard.
"But he's played on the wing once as far as we know this year, and I spend a good percentage of my time with our wingers making sure that they understand what's needed of them as far as the defence is concerned.
"It's a massive cog to the defensive system, you've got to be able to get that right and you would think experience helps you to do that.
"Playing at full-back is a little bit different, you can find your way into the game. As a winger you've got to find your way within the system to get yourself into the attack as well.
"So it's a tough ask but the quality that he's got I wouldn't put it past him that he'll have a good performance."
Meanwhile, Farrell confirmed flanker Tom Croft (toe) and inside-centre Jonathan Davies (general soreness) will both play on Saturday night despite sitting out Friday's captain's run.
"It's a funny old week obviously because of the game on Tuesday so we decided to have a double day yesterday, a really intense, physical session," Farrell said.
"Tom's just got a bit of inflammation within his toe but it's nothing to worry about whatsoever.
"He trained yesterday and got through the two sessions and the right thing to do is to give him a rest so he's right for tomorrow."
"Jonathan Davies didn't train either because of the intensity of the two sessions (on Thursday) ... but it's just stiffness that's all, so he's fine."
Wallabies number eight Wycliff Palu is also expected to play despite missing the Wallabies' final training run at Suncorp Stadium as he continues to battle a knee injury.