Farrell looked a shadow of his normally assured self in his first start of the season, missing four of his five penalty attempts.
The 20-year-old needed former England fly-half Charlie Hodgson to spare his blushes off the replacements bench with two second-half penalties to earn Sarries a 9-9 draw.
With Farrell's rival for the England jersey Toby Flood kicking nine points for Leicester, the pressure appears to be on the Sarries player but boss McCall is not concerned.
"Owen's not had much practice recently," McCall said.
"He's had a small groin injury which has stopped him practising as much as usual and it's very rare he has a day like this.
"He's a magnificent player for us but every man has the odd bad day at the office and I know he has the strength of character to come back.
"He's the sort of player who will use a day like this to bounce back stronger so I'm looking forward to that.
"I think it's definitely a case of two points dropped here as we missed plenty of opportunities.
"We came with the intent to play. If the breakdown isn't policed at all you're going to get a game like that with two teams defending so well.
"Leicester were penalised at the breakdown but not enough I don't think.
"They were the team hanging on in the last 20 minutes of the match, we were dominant in most areas even if that isn't reflected in the scoreboard."
Flood's three penalties, plus one in reply from Farrell, saw the Tigers lead 9-3 at the break.
Hodgson restored parity with two quick-fire three-pointers and he should have won it with a late drop-goal attempt.
Flood also had a chance to seal the win with a drop goal effort from the last kick of the game, but Tigers director of rugby Richard Cockerill was not in the mood to point fingers.
"We could have won it at the end, they could have won it at the end and these games tend to be close between the two of us but it wasn't a great spectacle and there were a lot of mistakes from both sides," he said.
"In the first half the lack of them kicking their goals helped us out a little bit but we need to look at our discipline in our own half.
"But that is two points we didn't have before the game so that's 12 points from three games and it was a tough game away from home so we will take it and move on.
"There will be a lot of teams who will play Saracens and get nothing. We have two points and we will take that, which is a positive.
"We did some good things but need to take our opportunities a bit better."
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