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MCC Analytics: Is Kristijan Kahlina a Top 5 MLS Goalkeeper?

Written by: Daniel Wicker

This is the start of what we hope is a regular contribution to Mint City Collective's ever-growing content that takes a look at advanced metrics, assesses Charlotte FC's performances as a collective unit, and evaluates its players. We'll also use the incredible databases available to the public to explore potential transfers, scout opponents, and trash talk the competition. But let's take things one step at a time.

While the club has been years in the making, and the squad has finally come together and earned their first clean sheet, the data is only just coming in, and the sample sizes are still incredibly small. With that in mind, it's important to point out we're working with the first five matches of data, and it's too early for any substantive predictions. For now, we'll have to stick to hot takes and using data for confirmation bias while we enjoy more Charlotte FC matches and wait for the season to play out.

As the squad continues to learn the system of Miguel Angel Ramirez in its inaugural season, Kahlina has had to bail the team out for defensive lapses, facing a league-leading three penalties and watching on as an Efraín Álvarez wonder strike finds the top corner.

The most robust dataset we have to analyze Charlotte FC thus far is the goalkeeping performances of Kristijan Kahlina. While he's certainly had his share of impressive moments and remarkable saves, we're going to take a look at the first month of performances and see how he's performed compared to his peers in the MLS. 

CLTFC’s goalkeeper Kristijan Kahlina     source: Charlotte FC

Because we're working with only 5 weeks of data, and even then, not all clubs have used the same keeper for all 4-5 matches, we'll be using squad goalkeeping data. Luckily Kahlina has played every minute of Charlotte FC's first five matches, but this will prevent even smaller sample sizes from presenting as outliers (e.g. Dayne St. Clair's recent burst onto the scene). All data used for this article are pulled from FBref.com and are provided by StatsBomb.

While simpler statistics like shots on target (SoT), saves, and save percentage can be useful, they can often be misleading when taken out of context. For example, a goalkeeper that faces more shots will concede more goals, but it's difficult to determine by raw data if this is a result of poor goalkeeping or a weaker defense that allows too many easy chances. 

As a result, we'll be looking at a metric called Post-Shot Expected Goals, or PSxG. PSxG takes into account the Expected Goals (xG) that a goalkeeper faces and evaluates how likely the goalkeeper is to save the shot. When we plot this with Goals per 90 (the number of goals a team concedes per 90 minutes of play), we can evaluate the quality of shots that teams are allowing against the goals that their goalkeepers are allowing. 

Before we jump into interpreting the graph, one critical caveat I want to make for this particular metric is that PSxG includes penalties. StatsBomb values a penalty kick at 0.76 xG, which is especially relevant for an analysis of Charlotte FC’s performances thus far as they have conceded 3 penalties in their first 5 matches. Taking this into consideration, CLTFC’s penalties (valued at 2.28 xG) account for nearly a quarter (!!!) of their accumulated PSxG (9.5) allowed this season.

Goalkeepers in the middle of this graph who are above the trend line are the best performers. They often face, and save, above quality shots. The standout players are the ones highest above the line. While there are a variety of hot takes we could make from this graph (e.g. Seattle's Stefans are #good, is Guzan dropping off?, etc.), we'll stick to interpreting what this means for Charlotte FC. 

As a lot of fans have noticed, Kahlina has been one of the top performers for the Queen City club through their first five matches. Charlotte FC's PSxG per 90 minutes is 1.9, meaning that, based on the shots they've allowed, they should concede 1.9 goals per 90 minutes. That being said, their goals per 90 are below that at 1.4. In terms of outperforming the shots on target he faces, Kahlina is well within the top 5 keepers in this very young MLS season. But what happens when we exclude penalties and look at how Charlotte's number one has performed against just shots in open play?

PSxG per shot on target (PSxG/SoT) measures the likelihood of a goal per shot on target. Higher values suggest that the shots on target a goalkeeper faces are more difficult to stop and more likely to score. PSxG/SoT also excludes penalty kicks. PSxG +/- per 90 measures a goalkeeper’s performance against their expected goals per 90. As an example, the goalkeepers in the top-right quadrant face harder shots (high PSxG/SoT) and often outperform and save the high-quality shots they face (high PSxG +/- per 90).

When we exclude penalties and look at how Kristijan has performed in open play, the data offers some interesting context to Charlotte FC's performances. Based on PSxG +/- per 90, Charlotte's shot-stopper is a top 3 goalkeeper in the league thus far. While it's still very early in the season, and it's hard to make definitive statements, the numbers support what we've seen on the pitch–Kristijan has been nothing short of spectacular.

However, the quality of shots on target Charlotte FC has seen is in the bottom half of the league, meaning the shots taken against Charlotte FC are easier to save. There are a couple of ways to interpret this. The optimist might look at this and say, "Charlotte's defense is performing really well, and even when they let a shot through Kahlina has been a top goalkeeper in the MLS!" Whereas the cynic would say, "Krisitjan has looked solid so far, but he hasn't really been tested yet. Can he do it on a cold, rainy night in Seattle?"

The reality is probably somewhere in the middle, and that's an altogether promising sign for this new club. Kristijan and the Charlotte FC backline have been solid, allowing few quality shots from open play, and Kahlina handles them well when called upon. The data also suggests the obvious–the penalties have been costly and have marred otherwise strong performances from this well-organized side. As Charlotte FC continues to develop as a club and build its identity, it'll be most important for them to cut out the mistakes and stop conceding penalties. I think it's also important to point out that, while Charlotte are not allowing high-quality shots, they are close to the top in shots on target allowed per 90. A team with an in-form, top striker might not be as forgiving as their previous competition.

All that said, the foundation is there for Charlotte FC to become a highly competitive team in this league, and that's in large part thanks to the heroics of Kristijan Kahlina. 

I hope you enjoyed this early look at Charlotte FC's goalkeeping performances! I look forward to updating this project as the season progresses and exploring even more in the months.

 If you enjoyed this, be sure to follow our new Mint City Analytics Twitter account @MC__Analytics.

 

 

 

 

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