When Youssouf Mulumbu slowly put his shirt back on at Rugby Park and acknowledged Kevin Clancy’s yellow card, the expectation was that the impressive midfielder’s goal would spark some fire in Celtic’s belly.

With 20 minutes of the game still remaining, the prediction was a bombardment would ensue.

In some ways it did. Just not at the goal most would have believed.

After that opener Kilmarnock had three cracking chances to bury the game. They scorned them all but there was a feeling, confirmed by Brendan Rodgers’ own observations after the game, that Celtic could have played all day without breaching Killie.

"We could've played here until midnight and not scored. We weren't really threatening," Rodgers said.

"We were disappointing. Defensively, we were a bit passive at times, even though we didn't have so much defending to do. We can blame injuries, we can look at the pitch and all sorts where it's very difficult to play, but the bottom line is we weren't so good today. It was a very disappointing result."

And that must be the concern for this season’s Parkhead team.

There is no panic button required to be pressed for a team who continue to hold a firm grip of the league title with an eight-point lead over nearest rivals Aberdeen. A League Cup has been successfully defender and back-to-back Trebles remains a distinct possibility.

It has to be said, too, that in some ways the staccato nature of Celtic’s campaign this term brings into sharp focus the magnitude of what was achieved last season as Rodgers oversaw an unblemished domestic record.

The defeat to Kilmarnock was only the second domestic defeat for Celtic since Rodgers arrived at the club, the other of course coming back in December with a sobering afternoon at Tynecastle.

But what is difficult not to notice is the lack of fluency and rhythm about Celtic this season compared to last.

They swashbuckled their way to the title in Rodgers’ inaugural campaign, knocking down long-standing records and stats along the way. 106 goals scored was a record number in the league in the Premier era and there was a ruthlessness in the manner in which teams were dismantled.

With 12 league games remaining, Celtic have hit 54 goals so far underlining the differentials up front between the two seasons.

This term has been beset with injuries – the groin problem suffered by Dedrcyk Boyata and the ankle injury picked up by Kristoffer Ajer during Saturday’s game takes the Parkhead side to 11 players jostling for space in the treatment room – but even so, the bite that spooked so many teams last year hasn’t been nearly so intimidating this time around.

Moussa Dembele’s future for the next few months was assured the second Leigh Griffiths pulled up with a calf strain last weekend, but the French forward is yet to hit his stride and show the same streak of form that made him so deadly in his inaugural campaign.

Not that he is alone.

Scott Sinclair started Saturday’s game on the bench but came on to take over from Ajer ten minutes before the interval. His impact, though, was negligible and given just how pivotal both Dembele and Sinclair were to Celtic’s pace, aggression, menace and penetration last season, it is difficult not to feel that when they are not at their best the entire team suffers.

New boys Charly Musonda and Jack Hendry made their debuts against Killie. Hendry looked comfortable at the back for the most part, although it is inevitable going to take the youngster a bit of time to fully settle in.

Musonda showed flashes of grace with the ball at his feet – one chance slipped through to Sinclair springs to mind – but given the lack of first-team action this season, it will take a while for the 21-year-old to fully integrate into the team.

Musonda has been tipped to provide the spark and give a flat Celtic the lift they need, but he will require a bit of time to get up to speed himself.

Olivier Ntcham who has been promising for the club over the last few weeks was off the boil too against Kilmarnock, although it was he who came closest to suggesting a Celtic goal. The midfielder has one free-kick which grazed the roof of the net in the opening period and another which was parried by Jamie MacDonald as Celtic chased their way back into the game.

That the latter effort was Celtic’s only shot on target told its own story of a frustrating afternoon.

And yet, it would be hard to be overly churlish about Kilmarnock’s win, the fist over Celtic since 2012.

The Rugby Park side were well worth it and it seems inevitable now that the chorus of voices urging the SFA to look closely at Steve Clarke for the vacant Scotland post should go up a decibel.

For Celtic, though, it is all about bringing the noise back.