Manager Neil Lennon insists there are no dressing-room problems at Celtic and is sure his players will rediscover their best form soon.
In response to internet gossip of a bust-up, midfielder Kris Commons turned up at training wearing a neck brace and bandages on his head and nose.
"There has never been a problem between myself and Chris. I'm bored of repeating myself on that," said Lennon.
"There is no dressing room unrest. I have a great relationship with them."
Scotland international Commons has only made eight appearances this season due to injury, illness and suspension.
But the 28-year-old is in contention for a place against Rennes in Thursday's Europa League tie at Celtic Park.
"He's a fantastic player and there's no doubt we're missing him," added Lennon.
"When we get him up to speed with match sharpness, it will be a real bonus because he's a threat for any opposition."
On the practical joke from Commons, Lennon explained: "That's us just laughing at all the speculation and rumour.
"When things start to go wrong at clubs like ourselves, people will start off rumours and look for things that aren't there.
"There's not a lot I can do about it. I can't stop the rumours on websites or forums but I know what goes on in-house and I know I've got a really good group of players that I'm very proud of.
"At the moment they are just not doing themselves justice."
Lennon was critical of his side following Saturday's 0-0 draw at home to Hibernian, which leaves Celtic trailing Scottish Premier League leaders by 12 points.
But he was in more forgiving mood on the eve of the meeting with Rennes, saying: "The players have been brilliant since I've taken over.
"Up until the St Johnstone game [21 August], we'd taken 125 points out of 147, so I know the players can do it and they know they can do it.
"It's a short-term problem but I need to rectify it very quickly and get them playing to their potential.
"The players are not far away from hitting the ground running. I know we can win games on a consistent basis because we've done it before.
"We're just missing that little ingredient at the moment and, once we find it, we'll be fine.
"We're still in every competition and we'll go for it hell for leather in all of them."