When is enough is enough?
When will Manchester United's demise this season be considered by the Glazer family to have become unacceptable? When should David Moyes start fearing for his job?
When is it time to sack your manager?
The time for apportioning blame for the slide has been and gone. The bare facts are that a team that won the Premier League title by 11 points last season are now seventh. Eighteen points off the top. Twelve off fourth place.
They've won the same number of points at home as Norwich and one more than Crystal Palace. They've scored the same number of goals at home as Fulham, who are bottom of the league.
It has caused some United fans to reach breaking point with their new manager.
At the beginning of the season, there was a feeling that Moyes wouldn't face any real threat to his job until at least a year-and-a-half into his reign.
It was thought that if things still weren't going well halfway through his second season, he would come under pressure.
But the board didn't bank on a season like this.
The problem for Moyes now is that he won't be allowed to limp towards the summer.
Between now and the end of the season, United face Olympiakos in the Champions League, Manchester City at home and a trip to Everton.
He also has cause to look nervously at the trip to Newcastle in April and Southampton on the final day.
Norwich and Sunderland, both battling relegation, are also due at Old Trafford.
It's conceivable that the humiliating defeat to Liverpool won't be the end of United's suffering this season.
The board gave the former Everton manager a six-year contract when he took over from Sir Alex Ferguson in the summer. But it would be remarkable—and irresponsible—if they weren't now devising a contingency plan should the situation continue to deteriorate.
Moyes is lucky in that he is manager of United and the match-going fans are unlikely to ever collectively vent their anger. That perhaps wouldn't be the case if he was manager of Chelsea, Real Madrid or Barcelona.
But he does have to worry about the brand.
United and the Glazers make millions from commercial partnerships every year. But sponsors want to be associated with success.
After all, "Chevrolet: The mid-table car manufacturer" isn't much of a slogan.
This is uncharted territory for the modern United, the one owned by the Glazers.
Since taking over in 2005, they haven't had to deal with the football side of the business failing. They simply let Ferguson get on with winning trophies.
As owners of the the Tampa Bay Buccaneers in the NFL, they have sacked head coaches. But this is the first time they've been under any pressure to make a change at United.
As such, it's difficult to know where they will draw the line.
That said, there is no money in struggling football clubs. And eventually, if there's no improvement, the Glazers will have to make a decision.
Some supporters lost faith in Moyes after the defeat to Stoke in February. For others it was Sunday against Liverpool.
But where the Glazers draw the line is what matters most. And every set-back between now and the end of the season brings that day closer.