CARDIFF, Wales -- Liverpool have done their bit, but if Jurgen Klopp's team are to end the club's 29-year wait to become champions of England again, they now really need a favour from their biggest rivals. And therein lies the crucial weakness in Liverpool's title ambitions: their hopes and dreams lie in the hands of a listless Manchester United.

A team requires many elements to become Premier League champions, and considering Liverpool are on course to end this season with 97 points, there can be no denying that Klopp has built an outfit with every single box ticked.

Liverpool are stylish, driven and tenacious, they have great players in every department, they score goals by the hatful and keep them out at the other end. If they win their final three league games, against Huddersfield at home, Newcastle away and Wolves back at Anfield, they will end up with 97 points, second all-time to Manchester City's 100-point haul last season -- and a total which no club has ever amassed in a Premier League campaign and failed to end up as champions.

But as good as Liverpool have been this term -- Sunday's 2-0 win at Cardiff owed more to durability and persistence than stellar quality -- their Achilles' heel heading into the final three weeks of this season is that not even three more victories will guarantee the title.

For Liverpool to finish on top of the pile, they need City to fail to win one of their final four games, and every Liverpudlian is focusing on Wednesday's Manchester derby -- when City visit United -- as their best, perhaps only, hope of a slip. If United are beaten, will Burnley away, Leicester at home or Brighton away really be able to throw a wrench in City's spokes?

City have won their past 10 league games and have rarely looked like dropping points. They have also won on their past two Premier League visits to Old Trafford, and United, as Sunday's 4-0 humiliation at Everton highlighted, are nowhere near being in a good place right now.

Liverpool moved back atop the table with their win at Cardiff on Sunday. Mike Hewitt/Getty Images

But even though Liverpool have lost just once in the league all season -- at City on Jan. 3 -- City's incredible consistency has left Klopp's men, and their supporters, desperately wanting United to get a result on Wednesday.

"We have no influence on [Wednesday's game]," Klopp said. "It doesn't look like United ... what was the score today? 3-0? 4-0?

"We know City will be ready. We just hope United will be ready."

In a sporting contest, you cannot suggest that the situation facing Liverpool is unfair, but it is certainly unfortunate because it is difficult to pinpoint a weakness in Klopp's team. The fault line is that they have to rely on others, and Klopp and his players cannot control what happens when City play at Old Trafford this week, or in the three games after that.

"We just need to concentrate on our side," Liverpool midfielder James Milner, the scorer of the second goal at Cardiff, said. "All we can do is keep the pressure on by winning games.

"[City] know they have to be perfect as well. All we can do is win the rest of our games, hopefully it's good enough."

Yes, City have to be perfect because this is a season when being almost perfect will not be enough. This is arguably the highest-quality title race for 20 years, since Sir Alex Ferguson's Treble-winning United team held off Arsene Wenger's first great Arsenal side to win the league in 1999.

But these City and Liverpool teams may ultimately be contesting the best title race in history. Neither side is showing signs of blinking, and they have both been ruthlessly consistent in recent weeks, with Liverpool staying alive and keeping pace with City by winning their past six league games.

At Cardiff on Sunday, 24 hours after City had ground out a 1-0 win against Tottenham to reclaim top spot, Liverpool found it tough against Neil Warnock's side. The first half was tense. The pitch was bone dry thanks to Cardiff choosing not to water the surface in the final hour before kickoff, and it slowed Liverpool down.

But Liverpool's persistence paid off, with Georginio Wijnaldum breaking the deadlock by scoring from Trent Alexander-Arnold's 57th-minute corner. Cardiff should have equalised on 64 minutes when captain Sean Morrison produced a contender for miss of the season when his attempted header from six yards flew over the bar after hitting his back.

Luck was on Liverpool's side with that one, and they also benefited from good fortune when referee Martin Atkinson awarded a penalty after Morrison's grappling match with Mohamed Salah. Milner converted from the spot to secure the victory that moved Liverpool two points clear of City again.

So the ball is now back in City's court. A win on Wednesday will be a hammer blow for Liverpool's hopes, but United can put them back in control.

The problem is, Liverpool and Klopp have no control over how their traditional rivals will perform, so Wednesday promises to be an excruciating 90 minutes for everyone connected with the club.