The two sides meet for a title showdown at the weekend, with the Red Rose heading into the match looking to claim a Grand Slam title after extending their unbeaten run with a 18-11 win over Italy at Twickenham on Sunday.
Farrell feels that form is not important going into their battle against the Red Dragons.
"We don't talk about favourites. We've not got six days to make sure our preparations are spot on," Farrell told Sky Sports News.
"We've had our moments where we have played well and we are four from four, which isn't a bad place to be in.
"Everything is down to that last game and then form goes out the window. It will be another big step for our boys to go down there and handle the emotion and pressure on the day."
The meeting in Cardiff will see last year's Grand Slam champions host the 2011 Six Nations winners.