The Red Devils suffered one of the heaviest defeats in the club’s history which saw them drop to seventh on the Premier League table, eight points behind leaders Chelsea.
The pressure on manager Ole Gunnar Solskjaer has intensified in the aftermath of the defeat with some club faithfuls calling for his dismissal.
Rooney, who is Manchester United’s record goalscorer and current manager of championship side Derby County, has joined in the criticism of his former side’s display against Jurgen Klopp’s men.
"The Liverpool game wasn’t easy to watch," Rooney told reporters. "I’m seeing too many players not willing to run back, not willing to defend and not willing to put everything on the line for that club and that’s not acceptable.
"Those players need to be hurt, need to feel when you lose games how much it hurts you.
"There is a big responsibility on those players. They are world-class players, international players and a club like United need more.
"The players have to question themselves. It’s too easy for the manager to take all the stick when those players are being paid a lot of money to do the job and I don’t think they’re doing it well enough."
"Obviously there’s pressure on Ole - everyone can see that," Rooney added. "But I know Ole and he’s a fighter. He’ll keep doing the right things, believing in what he believes in, and trying to get more out of those players."
