Farrell is a more reliable goal-kicker and a more imposing presence in defence.
While the USA performed admirably in Brazil this summer, reaching the second round, the one area of the game in which they remain thin is reliable goal-scoring.
In normal circumstances, that comeback, triggered by Conrad Smith's brilliant individual try and Stephen Donald's reliable goal-kicking, could very likely have borne fruit.
"Ben has proved himself to be one of the most reliable goal-kickers and creative broken-field runners in the game and we very much welcome his extended commitment to the team.
They have the world's most influential captain, the best second-row pairing in world rugby, the best open-side, the best No 8, the best half-back, the most reliable goal-kicker, the most creative inside centre and the fastest, most dangerous wing in world rugby.
They also have reliable goal kickers in scrum-halves Dimitri Yachvili and Morgan Parra, a vital source of points in tight matches, while fly-half François Trinh-Duc does the basics well but has the flair and unpredictability to keep defenses guessing.
He is not the most reliable goal-kicker on the planet (his own England head coach Stuart Lancaster granted that accolade to Wales's Leigh Halfpenny this week) but he knows it and has been working in training with the past master Jonny Wilkinson's favoured guru, Dave Alred to put it right.
If they throw the ball around from the start they will probably toss away their chances of the title: Italy are ranked 14th in the world for a reason, suffering from an ageing population and without a reliable goal-kicker, but they showed at Twickenham last month that they will happily join in when a match turns Barbarian with the likes of Edoardo Gori and Luca Morisi adept at exploiting space.
"So we need a reliable goal-kicker and Dan Biggar is a superb goal-kicker".
In tight Test match rugby, possessing a reliable goal-kicker is paramount.
