He was recovering from a knee reconstruction when he signed and went on to miss the whole of last season after undergoing operations to correct a persistent toe injury and then a nagging back problem.
Farrell is yet to discover first hand the complexities of rugby union away from the training field and debate still rages as to his best position.
And yet, on this one man England head coach Andy Robinson is pinning many of his hopes leading into next year's World Cup defence.
Farrell was included this week in England's 40-man elite squad alongside Jonny Wilkinson, another injury-ravaged talent on his way back to the big time.
Barring the inclusion of Mathew Tait, it was otherwise an uninspiring, conservative selection made up largely of the established order.
Leicester's try-machine Tom Varndell has been relegated to the 15-man national academy squad after being taught a tough lesson by Lote Tuqiri on the summer tour of Australia.
There may be question marks over his defence, but Varndell is a genuine attacking talent who was left isolated as England failed to convert their mountain of possession into anything meaningful.
Robinson also decided against injecting his senior England squad with Saracens' dynamic David Seymour, a genuine open-side flanker who shone at the Churchill Cup and would secure a regular and swift flow of ball, or London Irish hooker David Paice.
England have 11 competitive Tests left before the World Cup - not counting the summer warm-up matches.
If, as Robinson indicated, the 40-man elite squad will "form the nucleus" of England's team for this season when exactly are these highly-promising hopefuls going to prove their World Cup credentials?
Instead, Robinson is looking towards Farrell and Wilkinson to bring the inspiration and creative quality England so desperately need.
Wilkinson's pedigree in the sport cannot be doubted. Farrell's comes with a major question mark over it, simply due to his lack of experience.
Jason Robinson broke into the England squad in his first season, but he arrived as a winger.
It took Australian international Mat Rogers three seasons before he was ready to play anywhere other than the back three.
Farrell will be asked to make the cross-code transition as a playmaker and perform a central role in England's World Cup defence all in the space of a year.
But if anyone is capable of responding to the challenge, it is becoming clear Farrell is that man.
The last year has been a wretched experience for him, but Saracens players report he has been a hugely influential figure behind the scenes.
He has brought new ideas, new training patterns, a fresh angle on traditional methods and a star quality to Vicarage Road.
If he can do the same for England, he may well provide the answer Robinson is looking for at inside centre and the RFU's expensive recruitment gamble will have paid off handsomely.
Farrell will, after all, be an unknown quantity in union terms come next year's World Cup. But it is one hell of an ask for the 31-year-old.