This was a testing encounter for Celtic, but not in the way they would have wished ahead of their Champions League qualifier against Shakhter Karagandy.

It was too similar an assignment, since Celtic fell two goals behind and had to rescue the outcome. A similar turn of events is required on Wednesday, since Celtic lost the first leg 2-0 to the team from Kazakhstan, but it will have dismayed Neil Lennon that some of his fringe players did not take the opportunity to impress.

Instead, his team relied on "the stalwarts, Mulgrew, Brown, Ledley and Matthews". Two of them scored the goals, but concerns mounted, too. Beyond an injury to Beram Kayal, the performances of Amido Balde and Virgil Van Dijk were a concern, although both are still adjusting to new surroundings.

"It was a mixed bag," Lennon said. "I was really disappointed with the first half, but really pleased with the character we showed in the second. If players are going to come into the team they have to perform. I don't want to be dropping points willy nilly like last season."

Inverness were sprightly and bold enough at times. Terry Butcher lamented a missed opportunity, but his side are still unbeaten and top of the table and he celebrated at the final whistle. "It's wonderful," he grinned. "We're just keeping it going."

There was relief first for Inverness. The game was never a chore for them, since it was played at such an obliging pace. Even so, they were careless in allowing Celtic to build a move down the right that saw Kayal hit a crossfield pass to Tony Watt. David Raven ought to have cut the ball out, but it ran between his legs to Watt, who then shot meekly from a good position into the arms of Dean Brill, the Inverness goalkeeper.

Inverness survived their lackadaisical moment. That alone ought to have been valuable, but within minutes the escape was even more worthwhile. It initially appeared innocuous when Aaron Doran collected the ball 20 yards out and towards the left corner of the penalty area, but the Inverness midfielder curled a shot beyond the reach of Fraser Forster and it hit the inside of the post on its way into the net.

Celtic looked fretful and one-paced. Losing Kayal to injury was not a significant hindrance, since Celtic were able to replace him with Joe Ledley. A run and shot by Watt, then Efe Ambrose's header, briefly stirred the home crowd, but the occasion could not be roused. A second Inverness goal only dulled the mood of the majority of the stadium.

Emilio Izaguirre failed to clear Josh Meekings' long throw, and Billy McKay attempted an acrobatic volley that skewed the ball across goal. Richie Foran was able to stoop forward to head it into the net at the back post, though, leaving Celtic aghast.

Frustration spread, and the home fans griped noisily when Forster only ambled to retrieve the ball at a goal kick. There might have been a sense of outrage at half-time, but it was thwarted by a timely intervention. Moments before the interval, the ball was worked out to Izaguirre on the left, and his cross was converted by Charlie Mulgrew, whose shot wrong-footed Brill.

Celtic were complicit in their difficulties. Their play lacked intensity and urgency, even when they were obliged to chase the game. Balde headed just over from Watt's cross, but otherwise laboured to make an impact.

Inverness showed quicker wits, and Doran raced upfield after reaching the ball ahead of Van Dijk, who ought to have commanded the situation given his physical advantage. The Celtic defender tracked him, and appeared to then clumsily bundle into Doran's back, knocking him over, but no penalty was awarded, much to the fury of Maurice Malpas, the Inverness assistant manager. "Aaron is adamant it was a penalty," Butcher said. "But if he'd shot he could have killed the game off. He could have squared it to Billy McKay."

The Inverness management team must have figured that a third goal was still required. They understood that there would still be dangers to overcome. Scott Brown provided the impetus, pushing a clever pass inside Graeme Shinnie for Adam Matthews to collect. The Welshman then turned back outside Shinnie before rifling a shot beyond Brill. Mikael Lustig might have scored before the end, but headed wide at the far post. "It's a point gained," Lennon said, which was a measure of the ask his players set themselves.