Former Ireland fly-half David Humphreys says the side's next two Six Nations games against Italy and Scotland are now "must-win" following the side's opening defeats by Wales and France.
Ireland had never lost their two opening Six Nations games but Humphreys says the Rome contest will not be easy.
"Farrell has to win the next two games," he told BBC Radio Ulster.
"Italy have shown enough in the past two games to give them a huge amount of confidence against Ireland."
The ex-Ireland fly-half says any thoughts over giving relatively inexperienced internationals more game time in Rome on 27 February are now likely to go out the window for Farrell as he chases an absolutely essential win.
After the game in the Stadio Olimpico, Ireland face a much-improved Scotland away on 14 March before completing their campaign against champions England in Dublin six days later.
Experienced half-backs Johnny Sexton and Conor Murray sat out the France defeat because of injury and Humphreys believes they have to return if fit.
"Andy Farrell will have to ask what team he needs to pick to win the Italy game, not what team does he need to pick to win the World Cup," he said.
Munster scrum-half Murray, 31, missed out on the France game with a hamstring strain and Ireland captain Sexton, 35, remained on the sidelines as he followed return to play protocols following a concussion sustained against Wales on the opening weekend.
Jamison Gibson Park and Billy Burns deputised for the duo, with the latter replaced early in the second half by Ross Byrne, and Humphreys says Murray and Sexton are still a level above their replacements.
"I thought Gibson Park played well but those two players (Murray and Sexton) are top-quality internationals. I understand the point about making the transition and looking at the World Cup but Andy Farrell has to win some games in this Six Nations.
"It is a huge dilemma. Not just for international coaches but for anyone involved in performance sport - you are judged by results, not just performance.
"When he first came into the job Farrell had the chance to put his own stamp on this team by making those changes. There is absolutely no doubt that Sexton and Murray are the best half-backs in Ireland by a considerable margin."
Ireland have to adapt to Farrell
While the defeat by Wales can be attributed to Peter O'Mahony's early dismissal and several individual errors, Farrell's men rarely threatened the French line and were undone by flashes of attacking flair by the visitors.
Humphreys, who won 72 international caps, says France "deserve credit" for their performance in Dublin but Ireland need to improve in attack if they are to move forward under Farrell.
"I thought France were the better team and they created some very clear try-scoring opportunities," he said.
"The biggest frustration he will have is that while Ireland had a lot of possession in the second half, they didn't really create any try-scoring chances.
"The one try they got was a French line-out which bounced into their hands. They have to go away and find a way of attacking against the best teams - like France or England.
"In the past under Joe Schmidt, the way his game plan was set out, he created those by how he trained and how he prepared. Farrell is trying to implement a heads-up, play what you see style of rugby but that is hard to do," he added.
"It is going to take some time for those players to adapt to that and you have to, with the possession that Ireland had, create more try-scoring opportunities than we saw against France."