In the final four minutes of the match Farrell, who featured in one Test against the Qantas Wallabies this summer, had two opportunities to put his side back in front.
But a penalty from just inside his own half dropped short of the posts, while a drop-goal attempt was charged down in the final stages.
However McCall insisted his no.10 should not be criticised for the two missed chances as his overall performance was exceptional.
"Owen was magnificent, unbelievable, the best player on the pitch," McCall told Sky Sports.
"He did everything - defensively, offensively, goal-kicking, everything, and doesn't shoulder any of the blame. He was brilliant.
"We had a couple of chances in injury time, Owen's penalty was pretty close but I thought he had an unbelievable match.
"Toulouse are a very good team and we had to fight really hard in defence. For an hour we controlled them pretty well."