Despite the late change that pushed Alex Goode into first five-eighth, Liam Williams to fullback and David Strettle onto the wing, it was a case of no Farrell, no worries, for Saracens who led 22-13 at half time and then kicked on to book their Champions Cup semifinal against Munster at the Ricoh Arena in Coventry on April 20.
This was the first time Scotland had two teams reach the European quarterfinals but a 70th minute try from Irish wing Keith Earls and the Tyler Bleyendaal conversion proved enough for Munster to end Edinburgh's hopes with a four point victory at Murrayfield earlier in the day.
While rank outsiders to upset Saracens, Glasgow were, however, expected to put up a much more competitive effort for their passionate travelling supporters.
After scoring first, they then had no answers.
The power of the Saracens pack was on full display with Billy Vunipola, Will Skelton, George Kruis, Maro Itoje and man of the match Jaime George bending and breaking the Glasgow line throughout.
With a line up like that, it is no wonder there are questions about Saracens' salary cap payments.
Glasgow were constantly stretched on defence; they didn't deal with the high ball well and they struggled to build phases on attack.
The grim performance left Rennie deflated.
"Hugely disappointing," Rennie said. "We got a hiding from a team that choked us. Their kick chase game was good ours was poor. They camped down our end and they forced a lot of errors in regards to our defensive screen. They were slick. You can't put on a performance like that against a side like Saracens and hope to get a result.
"The difference between our competition [Pro14] and the English Premiership is minimal. They're a good side and they played really well we were under par and got pumped. That's what happens at this level if you're a couple of cogs off you can get embarrassed."
Glasgow's underwhelming afternoon was summed up by Stuart Hogg. The usually brilliant fullback, returning for his first outing since suffering a shoulder injury in Scotland's second Six Nations match against Ireland, missed touch from penalties and kicked out on the full three times.
"He'll be disappointed with his kicking game," Rennie said. "All those little things add pressure but he wasn't alone in that. We'll forgive him and I imagine he'll be better for the 80 minutes under his belt."
Munster should provide much more resistance than Glasgow offered but Saracens today showed the variety to their game. They scored down the short side, and out wide. They regularly got in behind Glasgow to generate quick ruck ball and they also struck with the rolling maul.
McCall described Saracens' paternity leave as "flexible" but he expects Farrell back on deck comfortably in time for the Munster showdown.
"He hasn't played for the last two weeks so I'm sure he'll be keen enough to get out there."
With this, their sixth European semifinal appearance in seven years, Saracens' record speaks for itself.
In this type of form, they will take some stopping.
"It's no surprise Munster go to Edinburgh and get the result they did. They're a European side that have been there and done it," McCall said. "We're really excited about the next two weeks."
In the other absorbing all-Irish quarterfinal, Leinster grimly held off inter-provincial rivals, Ulster, a 71st minute Ross Byrne penalty edging them 21-18 clear in Dublin.
The defending European champions now meet the winner of French heavyweights Racing 92 and Toulouse who square off in Paris tomorrow.
