Saracens suffered their first defeat at Allianz Park in the regular league season as they were beaten 22-13 by London Irish.
Three first-half tries from Irish sealed the surprise win which now gives Northampton Saints the chance to usurp Sarries at the top of the Premiership table.
Marcelo Bosch went over for the Men in Black but a James O'Connor penalty and tries from Matt Parr, Alex Lewington and George Skivington put the visirors in charge.
Schalke Brits added a consolation score late on but it was too little too late for Sarries who slippe to their second defeat of the season.
“The result is obviously disappointing” McCall said afterwards.
“I suppose with five minutes to half-time it was 8-10, there were two points in it and we would have the wind in the second half.
"Then you concede twelve points in that period and it gave us a mountain to climb.
“I must give London Irish a lot of credit today.
"I thought that they were exceptional, very physical, they held us up in the tackle time after time today and we didn’t respond the way we wanted to that."