'As mentioned before, and I´ve talked about this a lot over multiple threads, I´ve always felt we have a bigger problem in Mignolet than just his errors and fear of crosses. There was always this statement that he was a great shot stopper but I just had this nagging doubt in my mind that it wasn´t true. I know nothing of goalkeeping, I had no way to present that as an argument that I could support other than to say "I disagree, I think he isn´t"... which isn´t much of an argument.
Then this summer I got access to some good expected goals data for the first time. Not one of those basic ones that Ted Knutsen uses either to just give a vague idea - this guy went into far more depth with his workings including type of assist, type of shot, pressure on shot taker, etc. I realised that expected goals against vs actual goals conceded could be a way of then measuring how good goalkeepers are at simply dealing with shots. Of course commanding goalkeepers like Courtois will actually reduce goals due to preventing shots in the first place. But at least I had something to try and either verify or quell my fears.
When I ran every team in England´s expected goals vs actual goals numbers, all the expected top keepers (e.g. De Gea, Lloris, Cech, Courtois) come out as performing above averages. Mignolet comes out in the bottom 3 in the league. I run them for other leagues, the top keepers rise to the surface (e.g. Oblak, Neuer, Navas). I run all seasons I have data for in England and year on year, Mignolet is in the bottom 3 in the Premier League. In fact the only goalkeepers who have an individual season worse than Mignolet does consistently is Guzan, Fabianski and Boruc. When the data is grouping Mignolet in with those names and grouping together the likes of Neuer, Oblak, De Gea, Lloris at the other end of the scale, you know you have a problem. Karius was creeping into the Neuer group the season we signed him.
I also came across a study of the average zones on the pitch goals are scored from and comparisons for each team to the average. Liverpools stood out simply because we concede goals for long range and angles far more than average. The only similar team was Man City when they switched from Hart to Bravo. In terms of expected goals they went from having someone who performed a scratch above average to someone who would be capable of hitting Mignolet numbers over the course of the season, although with Bravo he was never historically that bad and so part of that is likely the whole foreign keeper adjusting to more physical league with twice as much crosses per game. Likewise they went from conceding goals in a tight circle around the goal to conceding from almost anywhere in the box. Although still it wasn´t as large an area as Mignolet concedes from.
So, if this information is correct - and I have subsequently seen it corroborated by two other analytics sites - it points to two things.
hen when you put Karius under the microscope, he is (or was when signed) one of the strongest young goalkeepers in europe. He also has one of the quickest releases of the ball in the top leagues, compared to Mignolet who once held the ball for 22 seconds against Bordeaux. Karius kicks and throws are also much further than Mignolet also. He also favours throwing over kicking to launch quick attacks. I imagine, for a coach who wants to hurt teams in transitions, having a quick thinking goalkeeper is preferable to one who holds the ball until the opposition can reset their shape.
As mentioned before, Karius is particularly strong in all aspects of shot stopping where Mignolet was weak. However, that is just shot stopping. It remains to be seen can he be a commanding presence? Also they both shared the same weakness - crosses! Oh, and Karius is also the 17th best goalkeeper in europe at saving penalties with ~35% save rate. Migs is 25% and Ward 13,3%.
So with all that in mind, it seems clear you want Karius in between the sticks as soon as he is ready, right? Well.. that should be if he is ready. I personally would make that switch now and just eat those errors that comes with playing in a new league/country just as United did with De Gea. But maybe the pressure would break him. Maybe he is not ready. Maybe never will be. Maybe Mignolet, in training with Karius, has adapted his game to better deal with long & wide shots better. Maybe that is why Mignolet now looks a lot more solid? I´ve no idea. But when 4 years worth of data is saying Mignolet is in the bottom 3 of his position every year, it´s certainly something to keep a close eye on.
As mentioned, Klopp hasn´t really put his spine in place yet, which is something all coaches like to do. I honestly think Karius will get a shot as #1 at some point and then we won´t look back. Everything we seen from him pre-Liverpool screamed future Neuer. That is the path he was on. I expected a rough first season and got it. That doesn´t mean he will reach such lofty heights - maybe he just won´t be cut out for the Premier League despite looking potentially world class in Germany. My gut tells me we have seen Mignolet´s ceiling and whether Karius replaces him or not, he probably isn´t Klopp´s #1 long term.'