Just as everyone predicted, Liverpool have been deadly going forward but terrible defensively in the Premier League this season.Jurgen Klopp's side have scored 13 goals thus far but conceded 12 - the joint third worst in the league - meaning they have a goal difference of +1.In comparison, Liverpool's supposed title rivals, Manchester United and Manchester City, have shipped just two goals each.Here lies the reason why the Reds probably won't be challenging for the title this season: their defence simply isn't good enough.Klopp made the bold decision to not sign a new centre-back over the summer and it's come back to haunt him, with Dejan Lovren and Ragnar Klavan both making countless mistakes.Worse still is the fact Klopp had the chance to sign Davinson Sanchez and Kalidou Koulibaly in the transfer window but said no.According to the German, neither Sanchez or Koulibaly would have represented upgrades on his current crop of centre-backs. Ridiculous, right?It hasn't just been Liverpool's defence at fault, though, because goalkeeper Simon Mignolet has been similarly woeful in between the sticks.Mignolet was most recently to blame for Shinji Okazaki's goal during the 3-2 win at the King Power Stadium, which almost cost Liverpool victory.The Belgian was far too weak at a corner and allowed Okazaki to out-muscle him, much to Jamie Carragher's frustration.Speaking on Sky Sports, Carragher said Mignolet isn't "streetwise" enough and needs to toughen up to stop players like Okazaki from bullying him.The truth of the matter is that Liverpool need a new goalkeeper and perhaps Klopp will realise that when he finds out how many goals this season have been Mignolet's fault.A study courtesy of InStat has revealed that Mignolet's mistakes have led to five of the 12 goals Liverpool have conceded in the Premier League, which works out to 42%.

As you can see by the rankings, Mignolet is fourth when it comes to players who have been at fault for the most goals according to how many games they've played, which is pretty shocking.

Furthermore, he's the only goalkeeper in the 'top' 20, which only reinforces how he's nowhere near good enough to be playing for a title-chasing side.

Not that Klopp will actually do anything about it.