Farrell was a surprise selection at first five in the England following
injuries to Jonny Wilkinson and Olly Barkley but Catt has admitted
he would be doing most of the decision making in the pivot position for the crunch
match.
"I'll start at 10 and predominantly stay at 10," Catt told the BBC.
"Obviously with Andy's left foot, I think it's a vital part of our game," he added.
"It's a bit like myself and Olly (Barkley). We want to get us down in the right parts of the pitch and when we do that we can attack off it. It's a massive task for us but as long as we play down there anything can happen."
England coach Brian Ashton said the two players are likely to interchange throughout the match.
"As an educated guess, Catt will play 10 and Farrell 12," said Ashton. "I see them both as inside backs, mixing and matching during the game. If I didn't think they could do it, I wouldn't have picked them."
Farrell agreed with Ashton’s comments when interviewed earlier this week.
"The last few weeks the 10s and 12s have all been swapping in and out anyway, and we share the workload and responsibility," Farrell said.
"The way Brian likes to play, he likes his 10 and 12 to control the game between them. There is not that much difference, just a bit more responsibility at 10.
"When Olly went off during training on Tuesday, me and 'Catty' just sorted it out between ourselves.
