Dundee United midfielder John Rankin believes some of his teammates have "downed tools" during matches this season.
Tuesday's defeat to Motherwell left United 13 points adrift at the bottom of the Premiership.
"There are players in there that will wholly admit that things are not going their way, and when it is that way they down tools," Rankin said.
"The situation we are in, it's not acceptable and heads do go down."
Rankin says he has taken it upon himself to try and rally his teammates in difficult moments this season.
"You try and grab players by the scruff of the neck. Of course you notice it happens. That's what happens in football.
"We need strength of character at this moment in time. People who will stand up and fight. We need every player giving 100%. Letting your head drop is unacceptable.
"I'm not saying they don't give 100% because in our mindset we are giving 100%. It's affecting us all. This will affect livelihoods.
"The supporters are turning out on a Tuesday night after they've been at work all day. They're giving us a 100%. Did we give them 100% back? No we didn't."
Mixu Paatelainnen admits his job as United manager is on the line as he battles to save the club from relegation.
He was speaking for the first time since his chairman released a statement criticising the players.
"The chairman is the head of the club and he's totally entitled to say whatever he wants - so we get on with it."
Asked if his position was under threat after just four wins in 18 matches he said, "Always - we are judged by results and results have not been good enough."
Chairman Stephen Thompson released a statement saying the players had to fight to save their professional reputations as well as its status as a Scottish Premiership club.
"He mentioned to me that he was going to put a statement out - I didn't know exactly the wording of the statement.
"I don't think it's a surprise to anybody that he's not happy with the situation - because none of us are," he said.
"I'm sure the strong characters will go out there and try to prove everyone wrong.
"As far as I'm concerned I'm in the same boat as the players - we work together, we train together and it's a combined effort together.
"We knew there was a problem when we came in and unfortunately the ship hasn't turned as quickly as we had wanted and perhaps anticipated.
"If anyone says there hasn't been improvement since we came in, I totally disagree with that -there have been big improvements."