CELTIC have played four competitive matches this season and the contrast in their performances has been vivid: Champions League good, Clydesdale Bank Premier League mediocre.

When they needed a goalkeeper's error to secure a late win over Aberdeen on day one of their league defence manager Neil Lennon said their display had been "flat". When an even later goal was required to salvage a point against Ross County he described them as "pedestrian". Flat, pedestrian: these are early days but so far Celtic have vindicated suspicions that they will often find it hard to lift themselves and consistently play to a high standard in a title race devoid of competitive tension.

What is easy to dismiss is the theory that they came within 15 seconds of losing in Dingwall because their minds were on tomorrow night's assignment in Helsingborg. Anyone who witnessed how Ross County set about them could see that Celtic didn't have the luxury of daydreaming about their Champions League play-off in Sweden. County played with such verve and controlled aggression that they were in Celtic's faces from start to finish. Despite numerous injuries, nine internationalists started for the champions but midfielders Joe Ledley, Victor Wanyama and Biram Kayal were eclipsed by Richie Brittain, Stuart Kettlewell and Iain Vigurs, the engine of a County team now unbeaten in 37 league games.

Gary Hooper, Scott Brown, James Forrest and Ki Sung-Yueng should all be available to replenish Lennon's resources tomorrow night, although Wanyama will be suspended. Celtic's league form has been ordinary, rather than truly concerning for them, and there is reassurance in the fact they were much more impressive when beating HJK Helsinki 2-1 in Glasgow and 2-0 in Finland. Helsingborgs, a comparable opponent, will surely draw a sharper performance from Celtic given the squad's collective desperation to reach the group stage after a four-year absence.

"We weren't thinking about Helsingborgs," said Mikael Lustig of his countrymen. "The manager and the coaches made sure we were focused on County. Tuesday's game is different. Helsingborgs are pretty strong. They are on a really good run just now and have a lot of confidence. We are going to meet a very good team. Helsingborgs are better than Ross County. They didn't have a great start, but they have played really well recently and are scoring a lot of goals.

"This is a big game for both clubs. The money you get for qualifying is very important. That's especially true for Swedish clubs. If they can make millions it would be massive for them. I've heard they were really pleased to get Celtic. We are a big club and Helsingborgs didn't want to travel somewhere like Croatia and Romania. It's maybe dangerous to think we can go there and win by four or five. I don't think we will."

Celtic will have group football until December – either in the Champions or Europa League – and it is likely to be the new year before their focus is solely on Scotland. That, and occasionally resting players for bigger ties, may make them vulnerable to more of the sort of demanding interrogations they were subjected to by County. The travelling support may have chanted "that's why we're champions" when Kris Commons equalised, but that flattered their team. They didn't win the league by serving up the sort of display which left them seconds from defeat to a club with a fraction of their resources.

Other than a slight recoil about having to call it the Global Energy Stadium, everything else about the SPL matchday experience in Dingwall was superb. The ground was packed and noisy, and the compact stands produced a vibrant little arena. It's a proper football ground. The playing surface was excellent and County's hospitality and attitude second-to-none. When it comes to their team, the pursuit of Derek Riordan is understandable because their spirited play was not reflected in enough danger around the Celtic penalty area, although Brittain followed his excellent free-kick goal – the club's first in the SPL – with a later drive which thudded the bar.

There was no opportunity for Celtic to preserve energy for Sweden: County hauled them into a contest. The champions, though, deserved their late equaliser. Amid a tide of pressure Wanyama and Charlie Mulgrew hit the woodwork and Georgios Samaras ought to have had a penalty. The dam broke in the dying seconds when Tony Watt's low shot broke off goalkeeper Michael Fraser to the feet of Commons. He couldn't miss.

Derek Adams, the County manager, questioned why referee Craig Thomson added three minutes of stoppage time, but his choice of words was measured and it would be absurd of the SFA to take action. As for Fraser, he simply felt unlucky. "On a good day the ball spins away or one of the defenders clears it. Unluckily for me, Commons was on hand to score. But how many times do you say it about Celtic when you think you have got them beaten? I made a couple of saves and we had some good tackles and you think they might have run out of ideas. But that's what a good team does. They can still hurt you."