Liverpool have struggled to hit the heights of Slot’s first season in charge. They sit ninth in the table, 10 points behind leaders Arsenal, after winning just seven of their opening 15 games.
Salah has scored four times in 13 top-flight appearances.
Rooney said Salah was wrong to say “I don’t have to go every day fighting for my position because I earned it”.
The former England forward added: “Time catches up with all of us, and this season he hasn’t looked as his best, at his sharpest.
“You want to see him roll his sleeves up and say ‘ok then, I’ll show you’.
“To have the arrogance to say he doesn’t have to earn his place because he has already earned his place, you need to be at your best every week to try and stay in the team.
“If I was one of his team-mates, I wouldn’t be happy at all with what he said because this is where Liverpool need him most.
“If anything, he has thrown Liverpool under the bus with his words.
“He’s been absolutely incredible for Liverpool, but this was disrespectful to his team-mates, manager and fans.
“I would imagine he will be very quiet around the training ground and that will bring a negative energy in itself to the new players Arne has bedded in.
“I am sure over the next couple of years he will regret saying what he has.”
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