Simon Grayson has told his Sunderland stars that they will be sold unless they show a drastic improvement off the ball.
The Black Cats started well at McDiarmid Park but a defensive collapse saw they go into the break 3-0 down. Grayson, who had started watching the game in the stand, cut a frustrated figure on the touchline.
The second half brought an improvement as the Sunderland boss rang the changes but that did little to temper his anger at what he saw in the opening period.
Grayson has been insistent that his players must adjust to a different mentality in the second tier but fears some are not showing the right signs.
He said: "There’s certain players that are buying into the ideas and certain players that aren’t. If players are not willing to work hard for this shirt they can go somewhere else. I’m not prepared to work with players who aren't prepared to run and do the basics that millions would give their right arm to do. We have to address it and we will address it.
"I was disappointed because it has been coming a little bit anyway. If you look at the Bury game, we were too easy to play against when we were 2-0 down and it could have been 3-0.
"And then today, if you give good opposition chances then they are going to take them.
"No disrespect to St Johnstone but they wouldn’t be in the top half of the Championship, and if teams in the top half of the Championship get opportunities like St Johnstone got then it is going to be a tough season for us," he added.
"The only excuse I would make for the players is that they have had a tough week already but ultimately they have to do better without the ball."
James Vaughan missed a penalty on his debut but his manager was impressed by his hold-up play and work ethic.
His young substitutes also drew praise for their application in what was a tame but level second half.
Grayson said: "We were playing better opposition and for the first 15 minutes we played well, we won the penalty and Vaughany was brave enough to take it.
"We had some other opportunities in and around it, but it was the other side of the game that was disappointing.
"It’s no surprise that when the young kids come on, they run around, they show desire to run forward and back, to do everything that is required to make a successful team.
"The three biggest cheers from the crowd were when James Vaughan won two headers and then chased down a centre-half who put the ball out of play.
"That’s what the rest of the team have to do, and if they are not prepared to do that, they won’t be here.
"It was a little bit about concentration, but also desire and hunger," he added.
"That’s what it’s all about.
"All the best teams have the desire to run about, to run forward, to run back, to chase, to put their bodies on the line, and that’s how we will be.
"We’ve only been working for two weeks and I am still getting some points across, but we will certainly be working hard in the next three weeks to get it right."