Sexton is seen by many as the favourite to be the Lions' Test fly-half against Australia this summer, but England's skills coach Mike Catt believes Farrell is hot on the Irishman's heels.
Catt has worked hard with Farrell and rates him as a player of rare talent and temperament, qualities he has only previously seen in Jonny Wilkinson. Catt said: "I guess a lot of people are going to look at it as a head-to-head thing from a Lions point of view."
He continued: "Both played exceptionally well last weekend and it is another game for both to put their hands up and say: 'right, take me on the Lions tour'. Owen's mental toughness is exceptional. I haven't (come across many players like that). Wilko was one of them.
"He is such a focused individual, he is so good at blocking out all the hype and everything that goes with it. He won't worry if it is Dan Carter, Sexton or Ronan O'Gara opposite him. What we want from our 10s is that ability to play flat or sit back in the pocket and kick. It's about getting that balance right at Test level, that's where Sexton is so very, very good.
"Now, it's about making sure these young (England) guys see it too. We're focusing on the detail of how to break down defences and that is helping him. Owen's enjoying himself at the moment, he's buzzing like everyone else."
Farrell kicked 18 points in England's opening RBS 6 Nations win against Scotland on Saturday, but it was his enhanced attacking play which really caught the eye. Typecast by critics as a steady, kicking fly-half - a product of his Saracens upbringing - Farrell played flat to the line and showed a variety in attack previously unseen in England colours.
Farrell's man-of-the-match performance was helped by the presence of Billy Twelvetrees on his outside and was synonymous with England's shift in style. Forwards are now encouraged to pass before contact and offload from the tackle, to keep moving the point of attack and not allow the opposition defence to settle.
Catt's recruitment as skills specialist has helped head coach Stuart Lancaster layer that detail on to the game-plan foundations that were laid last year. Catt said: "They are slowly starting to understand about speed of running, tempo, that sort of stuff. That's the detail we've gone into.
"It did help with the speed of the ball which meant Owen could come on to the ball much flatter and bring everyone else on to the gain line. You've got to remember where this team's come from. It's only a year down the line and they're producing some fantastic performances. All credit to them. I think it's remarkable they've got this far."