Chris Sutton believes Martin O'Neill should step down as Celtic manager, with the former striker labelling the team a "mess".

O'Neill's side have suffered six defeats in their past 10 games, winning three, before the Europa League visit of Besiktas.

"The defeat at Falkirk (on Sunday) was no surprise to me," Sutton told BBC Radio 5 Live.

"Domestically Celtic haven't played particularly well all season, Europe has been a disaster. They're 35th in the Europa League standings, only a team from Armenia (FC Ararat-Armenia) is below them.

"The pressure is really on. I'm just sad for Martin O'Neill where it's all turning a bit ugly.

"Yes, I would (like him to walk away). I think that would have been the right decision, but Martin feels he can do the job.

"The fans will always love Martin for what he has achieved at the club, but a lot of fans do not like the way the team are playing.

"There's a debate in every area of the team about who should be playing. Celtic are a mess at this moment in time."

Former winger Aiden McGeady, meanwhile, says Celtic need victory over Besiktas to "get some dignity and respect back" after three Europa League defeats from three.

"I think the main thing for Celtic now is trying to save a bit of face in this competition," McGeady told BBC Scotland.

"We're seeing Celtic play against Europa League teams, who I wouldn't say are fantastic, and coming up well short.

"When Martin came back in for his second spell last season it was just about getting results and winning the league and hopefully the cup, which he managed to do.

"But when you're starting a season afresh and you've got time to bed in your ideas and style of play and having a full summer of recruitment, to still be playing the same way and having performances of the likes we've seen recently is probably the most damning thing."