Written by: Eric Li (https://medium.com/@eli1)
Mohamed Salah, the Premier League’s 2017-18 Player of the Season exploded onto the scene with a record 32 goals in 36 games. Although Salah has been a solid winger for most of his career, nobody expected this sort of superstar performance from him. The “Egyptian Messi” truly came into his own this year, and we’ll be taking a look into how Salah went from Chelsea’s trash to Liverpool’s long-sleeved legend.
Before hopping into the analysis, we’ll be taking a look at data collection in soccer, especially for aggregate match data over an entire season. Jump to the next section if you want to skip to the analysis.
Soccer data is not well organized nor is it easily accessible. Unlike the NBA or the NFL, data in soccer is extremely hard to come by. Most of the time, it comes under a proprietary license and is never released for free (see Opta). Other times, when the data is free to the public, it is extremely difficult to find aggregate match data and large amounts of valuable data (such as distance traveled) are unavailable.
Take the Premier League for example. In terms of website design, the Premier League has easily gone above and beyond, giving users free access to all previous matches and all recorded data. Their user interface is extremely intuitive and it only took a few clicks to find any aggregate statistics I was looking for. That being said, the website fails to support head-to-head data, such as the average possession percentage for Liverpool against Leicester and Southampton.
WhoScored is soccer’s foremost data website, however the selection of statistics are very sparse. Team data especially is relatively bare bones and requires a large amount of supplementary analysis to make useful. This makes it difficult to draw correlation conclusions in terms of how a team performs against certain conditions or in certain situations. In comparison, Basketball-Reference and NBA both allow for ease of access (either directly allowing for CSV downloads of data or copy-paste formatting) and contain tons of match-specific data that can be used to easily calculate any statistic you could want.
In order to perform this sort of statistical analysis without watching every match Liverpool played and comparing it to every match Chelsea played in the last two seasons, I utilized Python and a few of its packages (Selenium and BeautifulSoup) in order to scrape aggregate match data off of the Premier League’s website. The code is posted on my GitHub and can be easily edited to scrape other statistics off the Premier League’s website. This aggregate match-by-match data was supplemented by general aggregate data collected from WhoScored. With this, we can finally take a look at Salah’s statistics.
Salah won both the Premier League Golden Boot and the Premier League Player of the Season, and both awards were given for a reason. With 32 goals and 10 assists, Salah was number one in goals scored and 7th in assists. His aggregate goal contribution of 42 far exceeded that of any other player, with Harry Kane (Tottenham) coming in second at 32.
Salah took on the primary goal scoring role at Liverpool, and the club would have it no other way. With 4 shots per game, Salah was rocketing in 0.22 goals per shot, a staggering ratio when compared to that of the other top scorers within the Premier League. That being said, Salah did have a propensity to lose the ball, something he was not known for before his time on in England. Giving up 2.6 dispossessions and 2.9 bad touches per game, the scoring focused winger had blunders to match with his, and his teams, aggressive playstyle. With only 1.7 key passes to go along with those turnovers, Salah solidifies himself as a goal scoring machine, but not too much else on Liverpool’s starting squad.
Figure 1 A comparison between Salah and other top goal scorers in efficiency
To be clear, Salah wasn’t always this type of player. In 2016-17, he recorded 15 goals and 11 assists with the Roman soccer club. His dispossession and bad touches per game were at a much more acceptable 1.8 each per game, albeit with fewer minutes and appearances overall. Roma’s Salah was clearly more of a supporting player, dabbling in both setting up his teammates and scoring the ball when an opportunity arose. This major difference in statistics shows the clear transition of Salah from a natural winger to more of a scoring forward, and is an important part of Salah’s impact on the league.
Taking a look at Roma’s preferred system, we see that their most common formation utilized a 4-3-3 which often transitioned into 3-4-3 or 3-5-2 when attacking the opposing goal. On Roma, Salah’s primary role was to set up Roma’s monstrous forward, Edin Dzeko (the league’s leading scorer), in Roma’s 4–3–3 formation as the right winger.
Utilizing their height and aerial superiority, Roma advanced through the defensive line via long balls, converting at a staggering 60.5% rate with 38.7 accurate long passes per game, good for third and second in the league respectively. The 6’3” forward Dzeko won 3.8 aerials per match by himself. It was Salah’s role on the team to receive these long passes from his backline and feed Dzeko. Utilizing his elite speed, Salah wasable to control these through passes and utilize his craftiness to find Dzeko behind the line. In fact, Salah assisting Dzeko accounted for 7 total goals, the most by any pair in the league. Salah himself registered 11 assists, the second most in the league.
Roma would also attempt to find Dzeko with loftier long balls for the big man to pull down and hand off to Salah, who could easily cut ahead of the out of position defensive line with his speed. The only issue with Roma’s tactics was their reliance on the long ball. Below is a chart of the 2016–17 season showing each team’s reliance on the long ball. Although Roma falls only slightly above average, every team above Roma failed to place above 11th in the league, with the bottom 5 teams on this chart accounting for 5 of Serie A’s top 8.
The strategy is clearly unsustainable and difficult to play well, at least for teams besides Roma. Without Roma’s concentration of individual talent, it seems very likely that they would not have performed nearly as well with their current style of play.
The Liverpool Life
In contrast to his role on Roma, Salah joined Liverpool to become the focal point of their offense alongside Mané and Roberto Firmino. By employing an aggressive 4–3–3, Liverpool opened up the offense to allow Salah and Mané to be more creative with the ball. Firmino’s niche position as more of a facilitating forward, i.e. a false nine, gave the winger pair even more freedom to make dynamic cuts when attacking the goal.
Liverpool employed a very aggressive counter-press style of play. When the offense lost the ball, Firmino spearheaded the front three in an attempt to win the ball back, with Salah and Mané supporting behind him. Given the amount of pressure this press provided, Liverpool often found themselves in a counterattack position, with either Salah or Mané cutting past a vulnerable, out of position defense. The counter-press worked especially well for Salah, as the opposition was pressed into the wide space by Firmino and Liverpool’s midfield, opening up the half-space for Salah to work with following a botched pass or successful tackle. This would give any winger great scoring opportunities, especially someone so tricky as Salah is with the ball.
Below is a graphic clearly showing Liverpool’s fast-break tactics. The first 15 minutes of any given match were dedicated to pressing the opponent, with over half the team occupying the opposing half of the field. Once this precedent had been established, Liverpool dropped back 5–10 feet as a unit, luring the opposing defense to push up those extra few feet. In doing so, any subsequent dispossessions by the opposition resulted in a huge expanse of space for someone like Salah to sprint into. For the first half of the season, Liverpool scored 14 goals in the 15–30 minute portion of the match, the most in any section of the match.
Figure 2 Liverpool’s average player position during a match. Salah, Mané, and Firmino are 10, 19, 9 respectively
Similar to how Roma took advantage of Salah’s speed in surprising an out of position defensive line with long balls, Liverpool did the exact the same thing but on a more consistent basis. Instead of playing a few through balls each game, the club was constantly counter-pressing and looking for an opportunity to take back possession while the opposition was least expecting it. Moreover, the threat of Salah’s speed in a counter-press opened up the middle and left half for Mané and Firmino to takeover, two supreme scorers in their own right. In fact, Salah’s 10 assists tied for fifth in the league this past season.
Taking a look at the front three specifically, it is clear that Mané and Firmino actively worked to set up Salah when pressing. Mané and Firmino worked hard defensively in the counter-press while Salah sat back and prepared himself to attack the goal with the opportunities that the other two created for him. In fact, Mané and Firmino recorded 1 and 1.8 tackles respectively, while Salah only registered 0.3. Furthermore, Salah attempted 4 shots per game alone, as compared to 4.7 shots per game for Mané and Firmino combined. Both statistics point to Salah’s increased offensive presence for Liverpool, even in their counter-press system.
The counter-press strategy resulted in Liverpool maintaining possession much more than their opponents, oftentimes ending matches with 70% or more possession time. That being said, possession percentage does not necessarily correlate with winning. Below is a graph that shows possession percentage as compared to score differential for each of Liverpool’s matches. Based on the simple linear regression and data, it is clear that there is very little correlation. In fact, the regression in 2016–17 shows a negative correlation between the two statistics.
This idea makes more sense when we consider how Liverpool played. Their aggressive counter press strategy allowed them to maintain possession through the match, however the flexibility given to their fullbacks to push up the field and press wide left the team vulnerable to strategically placed through balls, a common tactic for more defensive teams such as Burnley and Manchester United.
Now how exactly does Salah fit into this trend? Taking a look at average possession percentage and total score differential, we see that Liverpool’s possession percentage actually dropped from 61.9% to 60.7% while their total score differential jumped up from 34 to 46. Clearly, Liverpool was successfully scoring more with less. Their shots per game were exactly the same across the two seasons, 16.8 in both 2016–17 and 2017–18. This implies that Liverpool was converting more shots, whether it be through creating better opportunities or simply having a better scorer on their team. Between Firmino and Mané, their total goals only went up by one. Somehow, even after trading Coutinho, who scored 13 goals last season, Liverpool increased their ability to score with the ball. This all ties back to Salah’s efficiency of shooting, even on high volume. Liverpool provided Salah the scoring opportunities he needed, and Salah was able to show the world what he could do.
Salah’s speed and ball skills have always been two of his greatest strengths. Plugging him into an already well-formed Liverpool squad allowed him to focus on finishing rather than creating opportunities. Moreover, the threat of his speed in the Liverpool counter-press opened up other opportunities for his teammates to score. Either way, the triple threat of Salah, Mané, and Firmino combined with the aggressive play-style Liverpool employed gave birth to soccer’s newest up and coming super star, “The Pharaoh” of Liverpool.