ON Thursday, Celtic will return to European action. For Scottish football, it is a rare dip into post-Christmas continental waters. For Brendan Rodgers' team, it is another opportunity to test their progression outwith the confines of their own domestic wall.

With it comes a formidable task, even in the less intimidating arena of the Europa League. Bayern Munich and Paris St Germain have been left behind in the Champions League domain while Rodgers attempts to navigate his way through the rounds of the Europa, but the initial hurdle – both in terms of team and the tie – is far from diminutive.

Russian outfit Zenit St Petersburg will come to Glasgow first looking for a foothold to take back home with them to the new Krestovsky Stadium. Owned by Gazprom, the state-owned Russian bank has been ploughing ridiculous amounts of money into Zenit for well over a decade now, transforming them from mid-table meanderers to four-time title winners who have only dropped out of the top three once in the last 11 seasons. In the Europa this season, they won five out of their six games - drawing the other - and stood tall as the group stage's top scorers with 17 goals.

Known for their hated fans and dubbed Europe’s most racist support by critics - in December the club were hammered by Uefa for a fan banner praising Serbian war criminal Ratko Mladic, meaning a part of the ground on February 22 for the away leg will be closed - the prospect of facing this side cannot be underestimated.

Garry O’Connor, the former Hibernian, Birmingham and Scotland internationalist, spent two spells in Russia with Lokomotiv Moscow and then FC Tom Tomsk, and he is under no illusions as to the arduous nature of what lies ahead for Celtic.

“Zenit were always a physical, strong team when I played them,” he said. “They try and play the right way, in fact they’ll try and play right through you. The club has a lot of money. When I was in Russia, the picture that was painted was they were the up and coming team. They were sponsored by Gazprom who were helping them bring in big managers, big players. You could tell back then they were going to be the biggest thing in Russia.

“I was with Lokomotiv but they and CSKA are two of the biggest teams in Russian football history, but you could tell Zenit were moving in the right direction. They’ve always been a formidable side, and that’s what Celtic will have to deal with. The away leg over there would alarm me. They’ll definitely need to get two or three goals at Celtic Park if they’re going to have a chance because over there it’s going to be so tough.”

The declaration from O’Connor that Celtic may need to be two or three to the good before they set off for their Russian adventure in the away leg may seem startling, but the 34-year-old offers an eye-opening glance at what will lie in wait when the Scottish champions touch down in St Petersburg as the home side’s supporters make their presence felt.

“The fans have a reputation over there, I can’t speak very good Russian so I couldn’t tell you what they were shouting half the time but it’s intense,” said O’Connor. “You look around though and they are loud, so many in the crowd have skin heads and it can be quite intimidating. That’s a lot what Russian football culture is like.

“When you go away to St Petersburg you know you are going to have to defend so well. They play with some pace through the lines, if they want to turn you they will keep pressure on you, and that’s what their fans expect. For them to be playing hard and make chances constantly.

“You have to go there and do what a team like Hibs would do at Celtic Park, just try and stay in the game. It’s just the way the fans want them to play, it’s constant attacking football. That’s what I found when I was over there as a striker against them, you’re having to come deeper and not play in behind so much.

“It’s all in the first leg, I can’t express that enough. It’s always an advantage playing away from home second. When I watch football and when I played in these types of games, you do well in the first leg and that gives you the advantage.

"It’s going to be a funny one because the Russian season starts to March. They haven’t got that competitive edge unlike Celtic. When you look at players who have been injured or rested, I always find it hard to believe that if their season doesn’t start for another month these guys will be able to hit the ground running straight away. It’s always difficult.

“Celtic are already playing and are competitive. Having said that, some players will feel fresh, but I do think Celtic should feel the timing is more in their favour.”

Of course, Celtic don’t have their selection problems to seek in defence. In attack, the prospect of going into the tie without Leigh Griffiths is far from ideal. Last month the man with 11 goals this term went off injured against Hibs and is unlikely to play a part over the two legs against Roberto Mancini’s men. Without him, the scoring burden will largely fall to Moussa Dembele, who has only scored once in his last nine games.

O’Connor is a former team-mate of Griffiths during their second spells at Easter Road, and is clear in his belief that the Scotland internationalist is the top striker at Celtic Park. However, he reckons Dembele, who only last month Rodgers feared his mind had been affected due to the speculation surrounding his future, can get his game head on when it matters to give Celtic a chance of progression.

“Brendan Rodgers will have to shuffle things about but I’m sure he knows what he can do,” said O’Connor. “He’s a top-class coach and manager. European nights at Celtic under the lights are special nights, but there’s a pressure to perform.

“Dembele isn’t playing so well, he’s off the ball. The thing is with Sparky, when you have the wee man on the pitch you always think you’ll nick a goal no matter who he is playing for or who he is playing against. If he gets a sniff of goal, nine times out of 10 he’s going to hit the target. He’s got better as a player as time’s gone on. Running in behind was never his problem but his holding up play and awareness have come on massively.

“With Dembele, I think his head has gone a bit. He needs to work hard and get back in. I know what it’s like to be distracted and have your head turned by things going on around you. Especially now with the numbers and figures involved. He could be thinking of what is waiting for him elsewhere with the crazy numbers that are being linked with him. Transfer speculation does get on top of you and I’m sure that’s what’s up with the big man at the moment. He should be ripping things apart. What a stage this will be for him to start doing it again.”