On the face of it, a visit to Paisley with an injury-affected squad on the back of an international week and just days before the journey to the Camp Nou seemed a difficult assignment, but four first-half goals made this a day to quickly forget for St Mirren.
Barcelona might not be quaking in their boots when they receive the scouting report, but the Parkhead club will travel with renewed vigour after a muscular, efficient performance which made light of the absences of Scott Brown, Kris Commons and James Forrest through injury.
Lassad, Kelvin Wilson and Adam Matthews will all provide more work for the club's physios in the next few days, but, fortunately for Neil Lennon, Efe Ambrose emerged unscathed after marking his maiden goal for the club with a piece of touchline acrobatics which would have graced the Olympic gymnastics competition.
"My heart was in my mouth – I had never seen him do it before," Lennon said. "If he had landed on his neck he could have been in trouble."
The Northern Irishman flew out in Dermot Desmond's private jet to watch Barca in action in La Coruna last night, having witnessed a performance which raised the bar and allowed Celtic to travel to Spain as confidently as any Scottish team could hope.
"I keep saying that is the best we've played this season – you look at the way we played at Motherwell and Spartak – but they've topped it again," he said. "We looked strong, athletic and some of our football was of top order. We know Tuesday is going to be a totally different game but if we can play like we did today, and impose ourselves at times, then we will be OK."
The five-goal haul was a fitting reward for an adventurous Celtic line-up which featured Gary Hooper in an unfamiliar role off the front. On a day which began with an anti-racism display, it was also a cosmopolitan selection, with Tony Watt one of just two Scots in the matchday squad.
The 18-year-old was an energetic performer all day and although he would have to wait until the 86th minute for the goal his display deserved, his threat was shown within seconds as he forced Craig Samson out to clear.
St Mirren conjured one great opening of their own before the roof caved in – David van Zanten's deep cross reaching Lewis Guy, whose shot skipped into the hands of Fraser Forster – but when it came the collapse was breathtaking.
There was no surprise it was Hooper who broke the deadlock, merely what part of the anatomy it went in with. The Englishman's ninth of the season came courtesy of his knee as he latched on to a cross from Lassad.
The second was more spectacular, in the celebration if not the finish. A Charlie Mulgrew free-kick was spilled by the unfortunate Samson and Ambrose – a scorer in midweek as Nigeria booked their place in the African Cup of Nations, which will keep him from club duty for a month – repeated the feat at club level.
Next, Paul Dummett miscontrolled a Matthews corner and Victor Wanyama guided in Celtic's third before doubling his tally with the best of the bunch, curling in a beauty from 25 yards.
Half-time arrived, but there was to be no Sweden v Germany- style comebacks here. Joe Ledley and Ambrose both had free headers to add to Celtic's tally. Substitute Miku looked lively and Wanyama rattled the bar with one header and saw another cleared on the line.
At the other end, Steven Thompson had several great openings but didn't work Forster enough. Just minutes were left on the clock when Watt finally got his goal, heading decisively into the corner from Emilio Izaguirre's delivery.