Farrell has made a first appearance at inside centre - the position England's coaching staff have identified as potentially his best position in union.
The former Great Britain and Wigan rugby league captain featured in the number 12 shirt during a friendly against Cambridge University earlier this week.
His previous appearances for Saracens this season had been at blindside flanker.
"Andy went fine on Monday night, and I said after the Cardiff match (last weekend) that he will be given opportunities at both six and 12," said Saracens rugby director Alan Gaffney.
"But the overall point in all of this is that he still needs to be given more time to adapt to the game.
"More chances will come over the next few weeks when we have a busy first team and A-team schedule.
"When he settles down, we will see which position suits him best."
Saracens will start against Bath on Sunday with a back-row of Hugh Vyvyan, David Seymour and Ben Skirving - while Paul Gustard provides bench cover.