Callum McGregor admits "disharmony" at Celtic is having an impact on performance levels.
The Scottish champions lost their first league match of the season away to Dundee on Sunday, but it was the third in which they have not taken maximum points as they fell to five points behind leaders Hearts.
There have also been huge disappointments on the European stage, knocked out the Champions League by Kazakhstani side Kairat Almaty, with one draw and one defeat in the Europa League so far.
It has all been done against the backdrop of fan protests against the board after a disastrous summer transfer window and with concerns about how the club is run in general. The latest protest delayed the game right after kick-off at Dens Park on Sunday.
McGregor admits such discord is having an effect.
He said: "I think there's a lot of disharmony which can make it difficult for a club like this. It's so used to winning and everything's great, and you're winning games, but again, I think from the outside it looks easy, and it's not easy.
"The reason why we win so many games is that we work so hard. So, really, it's a double-edged sword. When you come to this club, you have to sacrifice everything to be a success, and then you get to enjoy all the good days that have come over the last 15-16 years.
"It's not easy, and I think periods like this just show that it's not easy. If you come off the boil slightly, if you're not quite there and that disharmony is there, then it can be a difficult place to play football. Our job in the changing room and in the building is to try and make the team as strong as it possibly can be, to then come out and perform on the pitch.
"I think if we get that bit right, then a lot of the noise will start to go away because any wee days like this that we've had have usually helped galvanise the group and make everybody fight a little bit more to show people.
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"This is what it's like playing at Celtic. Everyone thinks it's great, you're winning trophies... you only win trophies if you're together and you're ready to fight and you're ready to run and minimise the amount of days like this, because at this moment in time, we're too easy to play against.
"We're giving up too many goals. It's as simple as that; we're giving up too many goals."
Celtic now face Sturm Graz in the Europa League on Thursday before a top-of-the-table clash with Hearts at Tynecastle on Sunday.
Their captain admits they must prove they can go and win those games.
"We have to, and we have to show that we can," he said. "That's a challenge for the players, and we'll speak about it.
"Ultimately, we have to do our talking on the pitch. It's alright for me coming out and talking, anyone else coming out and talking, but we have to start showing why we're a good team and can be the team that goes on to be the champions. It's a tough football club to play for. I've seen it over the years. We've been very, very successful, but it's because of hard work.
"There's no shortcut. We've got good players, but football doesn't work like that. The reason why we've been successful is because we're willing to fight and stick together and be a team. It's time for everyone to step up a level. I've still got no doubt that we're a good team, and it will click.
"We just have to click maybe quicker than it looks like at the moment.
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