CELTIC'S Europa League campaign is now in a period of hibernation for two months and they were put to sleep with a bludgeoning in Zagreb.

What ought to have been a meaningless game, given that they had already qualified for the round of 32 which is played in February, was given significance by the dreadful defending which allowed Dinamo Zagreb to put four past them.

The finishes were good, and Marko Pjaca's hat-trick was fine, but even having added three goals themselves could not camouflage Celtic's flaws. They are through as Group D runners-up having conceded 11 times in the group. They should await Monday's draw for the last 32 with trepidation as well as excitement. Their defending is nowhere near good enough in Europe.

It was freezing in Zagreb - two below zero - but there was a half-hour spell when Dinamo went through them like a hot knife through butter. In scoring four, the hosts took to 19 the number of goals Celtic have conceded in 12 European games this season: two against Astra, two against Maribor, four against Dinamo, five against Red Bull Salzburg, six against Legia Warsaw. Were it not for the general excellence of Craig Gordon, who again produced a handful of big saves, those figures would be even worse.

Virgil van Dijk, overpraised on the back of his untroubled domestic performances, was again at the heart of a back four which was overrun in a European tie. Efe Ambrose did little to add a sense of security and Gordon received too little support from his full-backs. Emilio Izaguirre was anonymous and Adam Matthews had a night so awful he was culpable in Dinamo's two goals in the first half and was then substituted in the second. Mikael Lustig and Jason Denayer were out injured but all of Celtic's back four were experienced, familiar faces.

The seven goals made for an entertaining, eventful game, and it all unfolded against the strangest of backgrounds. The Maksimir Stadium usually hosts one of football's noisier and most passionate supports, but not at the moment. The influence wielded by the Dinamo fan group, Bad Blue Boys, was evident from how empty the place was. Bad Blue Boys have organised a boycott in protest about Dinamo's poor European performances and the call was answered. The Maksimir can hold 35,000 but barely 5000 were inside and 1000 of them were Celtic supporters. The Dinamo team was read out by the stadium's public address announcer to total silence, not even a ripple of applause.

There was, to be fair, some chanting for both teams once play was under way. Celtic can expect a penalty from UEFA after a flare was discharged among their supporters just before kick-off. They were fined £21,000 in 2012 for setting off fireworks and displaying an offensive banner in a game against Udinese. Uefa's control and disciplinary body will doubtless take action again.

Dinamo had taken the lead when Arijan Ademi's shot was deflected to Pjaca in the box. He skinned Matthews before tucking a sweet finish inside the far post. Soudani had earlier put the ball in Gordon's net too, but had been correctly ruled offside. Celtic started slowly before beginning to put together some passing moves and building their way into the game. Nir Bitton was fouled just outside the area and when van Dijk took a shot from the free-kick the ball spun high off the wall and seemed to spend a lifetime in the air before dropping for Kris Commons to bury a header. Dinamo's defenders and goalkeeper ought to have dropped their heads in shame for reacting so poorly to the deflection.

Stefan Scepovic was back in the Balkans and back in the Celtic team. His last start had been in the away game against Astra more than a month ago. So far he has been a poor signing for Celtic, another of those strikers in the £2m-£2.5m bracket they can't seem to get right. Three goals in 13 appearances is not enough, although the one which put Celtic 2-1 up was well-executed. Commons smacked a free-kick on to the bar and, when it dropped, Celtic again reacted better than Dinamo, with Bitton heading it on and Scepovic hooking a shot into the net. He got himself booked for lifting his shirt over his head in his celebrations, revealing a t-shirt with a happy birthday message.

Dinamo equalised thanks to another deflection. Matthews made an absolute hash of getting rid of the ball in the box and Pjaca scored his second with a shot which went in off Bitton. A terrific Gordon save prevented Marcelo Brozovic from scoring another and he was sharp again to block a Soudani volley, but Dinamo were flooding over Celtic and the resistance did not last. Domagoj Antolic saw that Brozovic was totally unmarked and picked him out near the penalty spot, from where he scored with lovely volley. Better still was the strike which gave Pjaca his hat-trick, a rising shot inside Gordon's left hand post.

Celtic had conceded two goals in the first five minutes of the second half. No more followed, but Celtic could not claw the game back. Josip Pivaric put through his own net after a good run and cutback by Izaguirre, which give Celtic a late third, and then Liam Henderson and Scepovic both came close in a strong finish. But conceding four times is usually insurmountable. Dinamo's European campaign is over for the season. If Celtic's defending is not addressed the last 32 will be the finishing line for them, too.