Yet, a third centre-half in the form of Kristoffer Ajer must be factored into the takeaways from a day that will be recalled for many years to come. An afternoon that, with Rangers’ win at home to Aberdeen, means Neil Lennon’s men require to take a point from their trip to Pittodrie on Saturday to seal the club’s eighth straight league crown.
Ajer, defensive partner of a Simunovic now entirely revitalised and re-evaluated, had far from one of his better games on Saturday. The 21-year-old was troubled by an impressive Kilmarnock, as were his toiling team-mates. The Ayrshire side three times were thwarted by superb stops from Scott Bain in an encounter that witnessed them fail to earn a warranted penalty from referee Willie Collum in early on after Scott Brown nudged Eamonn Brophy in the box.
However, whatever might be thought of the shortcomings of the champions-elect in two months under the interim charge of Lennon following Brendan Rodgers’ Leicester City flit, in demonstrating his faith in the Norwegian and the Croat, the current manager has been more than repaid.
Lennon conceded Celtic are no more than “grinding” out results at the moment. Their inability to produce the free-flowing football with which they have typically fashioned hatfuls of goalscoring opportunities accounts for that fact. At the other end of the pitch, though, the combination of Ajer and Simunovic is making Celtic formidable in repelling opponents.
Another clean sheet on Saturday made for the 16th in their past 19 domestic encounters, and a fifth on the bounce since Ajer and Simunovic came together after Dedyrck Boyata was lost to injury. Earlier this season, the notion that Celtic could be so stout without either Filip Benkovic - the £13 million on-loan Leicester defender then considered a class apart from his peers but now consigned to the bench - or the out-for-the-season Boyata would have been considered laughable.
Now, though, there would be far few sleepless nights from a desperately difficult to please Celtic support if this pairing were to be entrusted with the Champions League qualifying campaign that will begin in July - an eminent possibility with Boyata set to depart under freedom of contract and Benkovic likely to return to his parent club.
Ajer has taken his game to another level across the season. Simunovic is exhibiting a confidence that seemed to desert him entirely in the final year of the Rodgers’ era.
“I’m really delighted for Jozo, the way he works every single day at Lennoxtown on the pitch and in the gym,” said Ajer of his 24-year-old partner.
“He’s a top professional and someone I’ve learned a lot from. To see him score the winner in the 67th minute, wearing number five, was just incredible.
“The way Jozo’s performing now tells you everything you need to know. He’s a top class centre half. He’s still young but is already extremely experienced and has played a lot of games. He’s a great leader for us back there.
“Our partnership’s working well. We’ve not conceded many goals in 2019 and we’re happy with that. We’ve been defending well and when we’ve needed him Bainy [Scott Bain] has been fantastic as well. “I think we’ve got a lot of centre-halves in the squad and every week there’s great competition for a place in the team. That’s one of our strengths, we have to perform every single week otherwise someone else will come in. Jozo and I have performed really well in recent weeks. However, we know that at Celtic you’re never better than your last game. We have to continue to perform.”
There is a weariness about Celtic now that, crucially, might not be found among the club’s defensive triangle of Bain, Ajer and Simunovic because all three haven’t had to haul themselves through the vast majority of the club’s 59 games. Fatigue doesn’t cut it as any excuse for sharp drop-off in Celtic’s performance level for Ajer, though.
“I don’t think it’s difficult at all [to remain energetic]. You play for so much at the end of the season and that’s why you play the whole season – to be in the position we are now. You just have to keep focused. We need to look to perform well against Aberdeen and in our last few games of the season. Every season the aim at this club is to win the league and we also have the Scottish Cup final against Hearts.”
It is surely the case that a treble treble will go on the line on that after of May 25 - the day, course, that McNeill was responsible for the most enduring image in the history of the Scottish game in the moment he thrust, glatorial-like, the European Cup above his head in the ancient-Roman style amphitheatre of the Estadio National.
As well as the physical rigours that may be catching up with Celtic, it must be acknowledged that the huge outpouring of affection for the man whose status in the modern-day Celtic is second only to Jock Stein made Saturday also a day to drain the emotions.
“Of course it was emotional for everyone,” said Ajer. “You could see how much Billy meant to the whole club, you could see the Celtic Way when we arrived, you saw his family, the Lisbon Lions legends coming. So of course it was a big, big day for the whole club. I’m just happy that we managed to get the three points.”
A typical pronouncement from a young defender with such a sensible and mature head on his shoulders, he is precisely the type of which McNeill would surely approve.