A couple of years ago, N’Golo Kante might have been the most valuable soccer player in the world.

In August 2015, Leicester City signed the relatively unknown French midfielder from Caen for £5.6 million. The season before his arrival, Leicester finished with 41 points. In Kante’s only season with the club, Leicester finished with 81 points, winning the most improbable championship in the history of modern sports.

Then, in July 2016, Chelsea signed the by-now-well-known French midfielder for £32 million. The year before Kante’s arrival at Stamford Bridge, the club finished with 50 points, by far the worst tally since Roman Abramovich bought the club back in 2003. In Kante’s first season with the team, Chelsea finished with 93 points, winning their fifth Premier League title. Leicester, meanwhile, held onto all of the other key contributors to their championship team, but without Kante, they almost slipped right back down to where they were before he’d arrived, finishing with 44 points.

Ignore any other context and it looks like Kante alone was worth something like 40 points a year. That’s obviously not quite true, but it certainly seemed like Kante was one of those rare players who could significantly elevate his team’s performance without putting the ball into the back of the net. And in the summer of 2017, a group of researchers from the University of Salford and University College of London published a paper that supported this very idea.

They created a number of models to determine a player’s “plus-minus” rating, that is comparing how a team performs when a player is on the field with how it performs when he’s not. These models are tricky and imperfect because unlike in basketball, most teams don’t spend a significant amount of time with their starters off the field; therefore you get things like Manchester City’s Claudio Bravo being the second-highest rated player in the world for the 2016-17 season. However, the results of the research also seemed to verify what everyone at Stamford Bridge and the King Power Stadium was thinking about Kante.

“The paper presents a method for estimating how important each player is to a team’s success,” Ian McHale, one of the paper’s authors, said over email. “For the seasons under consideration, Kante was found to be the player contributing the most to a team’s success. And this doesn’t just mean Leicester and Chelsea, but a hypothetical team made up of any set of players: Kante would contribute the most.”

Except, in the two seasons since then, something has happened that had never happened before … and it’s happened two seasons in a row: The team Kante plays for didn’t win the Premier League. In 17-18, Chelsea finished in fifth and last year, they landed third.

“Kante has plummeted down the rankings in the last 12 months, probably because he was played out of position for much of that time,” said McHale.

Much of the discussion surrounding Kante over the past year-and-a-half echoes what McHale suggests. Since Chelsea signed Jorginho, a relatively immobile player who needs to sit in front of the defense and constantly have the ball at his feet in order to be effective, Kante has been deployed higher up the field under both Maurizio Sarri and current manager Frank Lampard.