Angry Cardiff City fans turned up at the ground to show their disgust at the treatment of manager Malky Mackay.
Club owner Vincent Tan has reportedly told the Scot to either leave his job or face being sacked after he talked to the media about possible additions in January.
The Malaysian businessman was said to be angry about his comments after giving him £35m to spend in the summer.
However, his actions have provoked a backlash from Bluebird fans, who are increasingly concerned about the direction of the club under Tan after he controversially changed their kit colour from blue to red.
A gathering outside the ground chanted: "Don't sack Mackay, Malky Mackay, I just don't think you understand. If you sack Mackay, Malky Mackay, You're going to have a riot on your hands," while at the same time holding up banners reading "Tan out" and "Hate the Red, Love the Blue".
Sian Branson, a spokesperson for supporters' group Bluebirds Unite, is quoted in the Independent as saying: "We want to enjoy being in the Premier League, but we can't because the club is being run like a megalomaniac's toy. The fans have had a gut full.
"As a group we are trying to calm the fans, but there is only so long you can keep a lid on a bubbling pot. It's wrong because without the fans here, there wouldn't be a club. How can a man who, by his own admission, knows nothing about football talk about the style of play or send notes to Malky about which players should be playing?
"We feel sorry for Malky, who is the best manager we've had. He's done a great job and we don't want him to go. Tan came in with the money, which was great, and he could have been a hero. Instead he has taken everything we are and now he's taking away our manager."
Mackay has led Cardiff to 16th in the Premier League after guiding them to the Championship title last season.