They were 3-0 up and coasting, courtesy of a Kris Commons double and a Stephen McManus own goal, when Anthony Stokes took it upon himself to enliven the proceedings with a reckless kick on Keith Lasley's ankle that earned him a red card.
The Irishman was applauded off the field - his victim is something of a pantomime villain in these parts, and there may have been a whiff of retribution for a tackle here in October which put Adam Matthews out for several months - but the dismissal was the only blot on an otherwise good day at the office for the Parkhead side. This was their eighth SPFL clean sheet in a row,their best domestic defensive record since 1986.
"My initial reaction was just for the well-being of my captain because I thought it was a bad, bad tackle," said Motherwell manager Stuart McCall. "We don't carry a great deal of players and I thought it looked like a tackle that would put Lasley out for weeks, if not months. Fortunately, it's not done that. I think there is bad blood to Las from everyone that comes to this ground! If you remember last time out here there was a collision with Matthews that was accidental but that put him out. So the Celtic fans probably think back to that."
Visitors to the East End of Glasgow yesterday knew something had to give. While Celtic returned from Turkey keen to continue with their winning ways, Motherwell knew victory for them would equal a seven-match top-flight winning run, a feat they last achieved 81 years ago. The Lanarkshire side drafted in Zaine Francis-Angol for the injured Simon Ramsden, while Neil Lennon kept Amido Balde, Teemu Pukki and Nir Biton, all of whom impressed in Antalya, in reserve. There was no sign of contract rebel Georgios Samaras, ostensibly due to a knock.
Having spent much of the early season relying on late goals, Celtic have recently developed a habit of getting early ones. Yesterday, the minute's applause in memory of Bobby Collins had only just subsided by the time the hosts were one to the good.
Unsurprisingly, Commons both created and scored it. His quick pass to Stokes breached the offside trap, and when Gunnar Nielsen could only palm out the Irishman's attempted low finish, Commons had followed the play and could gleefully roll the ball into the net.
Charlie Mulgrew had been somewhat rudely shunted out of his central midfield berth to accommodate Joe Ledley, perhaps a sign that the Welshman will finally sign his new deal, but the Scotland international was nevertheless keen to get forward. He should have converted one Emilio Izaguirre cross, then tested Nielsen with a header.
Motherwell tried manfully - Lasley got into some feisty scraps with Scott Brown, and James McFadden displayed some fantastic touches - but Celtic were playing with a zest they couldn't live with.
James Forrest scampered through to send a low effort wide, and Virgil van Dijk slashed past after an outrageous double drag back, before the second goal arrived.
Again the Motherwell backline was too easily breached for McCall's liking. Mulgrew played Stokes through, before Nielsen brought him crashing to the ground. Commons stepped up to lash in his 19th goal of the campaign.
Fraser Forster, to this point a virtual bystander, made an unorthodox save from Iain Vigurs, before McFadden blew his side's best chance, finishing tamely against the giant Englishman from close range.
Perhaps spooked by the let-off, Celtic got back on the front foot. Stokes clipped the junction of post and bar, and it soon transpired that the only successful Motherwell finish of the day would be beyond their own goalkeeper. McManus was given a special ovation from his former supporters after his miscued clearance from Forrest's wicked delivery flew past Nielsen.
Then came Stokes' late challenge. "I thought Anthony made a genuine attempt to get the ball," said Lennon. "He was late and it's one of those that can be a red card when other times it's not. Normally I punish players for red card but I won't be punishing him for this one."