Celtic returned to the summit of the Scottish Premiership on goal difference after the intervention of Callum McGregor and Nicolas Kuhn ensured they maintained their unbeaten league start in a thrilling contest with a spirited Kilmarnock.

To say the defending champions were tested by a vibrant, impressive Kilmarnock side, would be the understatement of the season.

The expectation was that if Brendan Rodgers' side showed the levels they hit in the Champions League win over RB Leipzig on Tuesday, then this may have been far a more comfortable trip to Rugby Park than they often are.

It turned out to be far from it.

Derek McInnes adopted an alternative tactical approach, with two up top and Corrie Ndaba continually stepping out from the back to drive forward.

That, aligned with a relentless desire to take the game to their opponents, troubled Celtic throughout. Kilmarnock created so many chances, and will undoubtedly feel they deserved better.

A wonderful, cutting move almost gave the home side an early reward. Marley Watkins got in, and the striker clipped it past the imposing Kasper Schmeichel. Agonisingly for Kilmarnock, it clipped the post and bounded away.

Was it to be one of those days for McInnes? Yes, as it turned out.

Kyle Vassell then struck after a great turn but, as his shot angled towards the top corner, a deflection took it behind to Celtic's relief.

Kilmarnock's intensity was incredible but McGregor took charge just moments before the break, having been earlier denied by goalkeeper Robby McCrorie.

The Celtic captain built play and advanced his team up the pitch. When he found space, he waited for Idah to move and clipped in a cross that evaded his team-mate, and McCrorie, before nestling in the corner.

It was undeniably cruel on Kilmarnock.

They responded, though, and maintained their intensity, hemming in Celtic with Innes Cameron and Brad Lyons both going close. Then, when Matty Kennedy danced into the box, Schmeichel got low down to thwart him.

Kuhn ought to have put daylight between the sides when a one-two put him through, but McCrorie brilliantly saved.

The goalkeeper could not do the same a few minutes later. Alistair Johnston clipped a ball in behind and Kuhn seized on it, sprinting away, and flashing in a devastating finish. The German seems unstoppable right now.

Celtic took the points once more. Their quality ultimately told but this was by a distance their sternest domestic examination of the campaign.

Kilmarnock will barely believe this outcome. Their approach was brave, intriguing and full of desire. Two up top, and prepared to go man-to-man against Celtic's three-pronged strike force. It worked so well.

Celtic just couldn't build pressure as the home side continually probed at them, giving their backline no respite.

They were the better side for spells and came so close through Watkins.

Every element of their performance was bang on as they refused to let Celtic settle into any rhythm at all. Crucially, they just couldn't capitalise, denied by Schmeichel and dogged defending time and time again.

The concession of the opener was so unfortunate, but they still stuck to their task. Regular performances of this standard will see Kilmarnock rise up the table quickly.

You have to earn Premiership titles and Celtic delivered here in the most testing of circumstances. They adapted to what they confronted and got the job done

In complete contrast to their recent dominant displays against Aberdeen and RB Leipzig, this showed a different side to Celtic's character.

They were pushed and pushed to the limit but still emerged unscathed.

Captain McGregor was instrumental once more. He had gone close already before just seizing control to deliver the breakthrough.

It was fortunate but the way he calmly dictated Celtic up the pitch was impressive.

And what else is there to say about Kuhn right now? His level is off the charts and in key moments he has no hesitation.

Everything he touches seems to turn to goals, either directly or via assists. His development from last season is incredible.

Rodgers will be thrilled with the outcome but also likely by the manner of coming through such a grilling. They did so and stay very much on course.

Kilmarnock manager Derek McInnes: "I feel for the players. We've been the better team. Celtic have been getting so many plaudits of late but they didn't enjoy that.

"I don't think Celtic had any real control. The XG we had, the chances we created - twice as many as Celtic, twice as many touches in the box, twice as many shots - but ultimately it comes down to goals and moments.

"I'm disappointed for my players but a lot of what we wanted from the game today we got. We made it difficult for Celtic who have been swatting teams away of late."

Celtic manager Brendan Rodgers: "We had to deal with a lot of pressure and direct balls. But to keep a clean sheet and work that hard, especially after midweek, then show moments of quality to get goals, I'm very proud of the team.

"A year ago, that result would maybe have gone the other way. It was a real test of different qualities and we came through it so it shows the team is in a good place.

"Nicolas [Kuhn] is growing and developing. He is disappointed with the one he missed, but his run, touch and finish were sublime. Adding numbers to his game is one of the things we talked about and it's testament to him that he's done that."