London - Arsenal manager Arsene Wenger revealed he was contemplating a re-arranged fixture after the Gunners beat Cologne 3-1 in a Europa League opener marred by crowd trouble at the Emirates Stadium on Thursday.
The Group H fixture kicked off an hour late following chaotic scenes inside and outside north London club Arsenal's home ground.
Thousands of ticket-less supporters of German club Cologne arrived at the Emirates, with kick-off delayed by an hour in the interests of "crowd safety".
Police, forced into deploying extra officers, made five arrests after dealing with "disorder" at the Emirates as Cologne fans occupied home sections of the ground, with an estimated 20 000 supporters having travelled from Germany despite there only being 3 000 away tickets.
Arsenal fell behind early on to a brilliant long-range strike from Jhon Cordoba before bouncing back in the second half, substitute Sead Kolasinac equalising before goals from Alexis Sanchez and Hector Bellerin saw the Gunners to victory.
Afterwards Wenger said he was getting ready for the game to be postponed but was uncertain if the delayed kick-off was to blame for the Gunners' poor start.
"It's difficult to say," he said. "It was similar for Cologne but we had some problems to get off, to start, yes. I don't know, was it mental?
"We waited patiently in our dressing room but what was difficult for me was I had all kind of plans to think about at some stage."
Wenger added: "I had to think if we play tomorrow at what time do we want to play, do we play next week but they had the Bundesliga again midweek and we had a League Cup game midweek as well.
"But in the end at some stage I thought they would not play the game, because I can't see the police taking any risk," he explained.
"We live in a society of 100% security and I thought they would never take a gamble to play this game when I saw the images around the stadium.
"But I must say our supporters dealt well with the situation as well and there was no aggravation."
Wenger said Cologne fans had been "very clever" to get into areas reserved for home supporters.
"I don't know how they managed to infiltrate our fans and get everywhere but they did that very well. I don't know if they went through Arsenal membership, on the internet... they did very well."
One social media post appeared to indicate scuffles inside the ground, with Richard Conway, a BBC sports news correspondent, tweeting: "Koln (Cologne) fans fighting with stewards inside Emirates stadium. Group arrived in home end and fought their way into away section."
Cologne coach Peter Stoeger refused to be questioned on the actions of the club's supporters: "I have no comment about the fans," he said.
"I'm the coach, my job is the team, my job is football not the fans," the Austrian added.
Asked on the eve of the match if he had a message for the thousands of travelling Cologne fans, Stoeger replied: "Enjoy the pubs!"
Cologne are currently bottom of the Bundesliga table, having lost all three of their opening games in this season's German top flight.
But they qualified for the Europa League after finishing fifth last term.