Few players have divided the opinion of Premier League fans more than Arsenal's Granit Xhaka.
One of Arsene Wenger's final marquee signings, the Swiss midfielder arrived from Borussia Monchengladbach for a fee of around £35m to plug the gaping hole in Arsenal's midfield.
Santi Cazorla and Jack Wilshere's injury records were slowly getting worse and Francis Coquelin had fallen out of favour.
As for Aaron Ramsey, his best year at Arsenal came alongside a player similar to Xhaka in Mikel Arteta, a deep-lying playmaker that would emphasise control over destroying.
However, his time under Wenger was typified by the fact that he was rigorously exploited by opposing midfields and forced to constantly defend - a skill he isn't particularly great at.
But under Unai Emery, Xhaka has gone from a clunky liability to the key man in Arsenal's midfield.
To put it simply, the Gunners are regularly impotent without the Swiss man in the middle of the park, especially against high-calibre opposition.
A statistic which puts his importance into perspective is that the last 18 times Xhaka has played 90 minutes in midfield in the Premier League, Arsenal have lost just once.
His passing is daring, it strikes fear into the opposition and he's the man that links the midfield with Arsenal's star-studded attack when the team's back is against the wall.
XHAKA'S THE DEEP-LYING SUPPLY LINE
Lucas Torreira's addition to the side has allowed Xhaka to transform into the midfielder he wants to be, orchestrating the attack with freedom and feeding those in front of him with speed and precision.
No one in the Arsenal side comes anywhere near his average of 79 passes per Premier League game, with centre-back Rob Holding the nearest competitor on 61.4.
Xhaka's average of 5.7 long passes a game is also the club's highest - Petr Cech, a goalkeeper, sits in second with 5.4.
Here's where the Swiss' importance lies, he's the conductor, the Jorginho of this Arsenal side, but he mixes up his passing range far more than the Italian.
Like Jorginho, Xhaka will never rank high in the assist chart - he has just one in the Premier League this season - but his bravery with his passing is what galvanises Arsenal.
When the team are struggling to move up the pitch, Xhaka can spray an inch-perfect long pass to unlock the chains. When Arsenal have the ball, he can control and break the lines of the opponent time and time again.
TOO MUCH FOCUS ON HIS WEAKNESSES
Let's make it clear, we are not saying Xhaka is a player without limitations. In fact, he possesses three key ones.
His lack of defensive nous is clear, his pace is non-existent and he's pretty poor when asked to use his right foot.
Had he chosen to be a centre-back, a winger or a striker, Xhaka would probably struggle to make it as a professional footballer.
But in the role he plays in this Arsenal setup, those limitations haven't held him back and why would they?
Some of the greatest midfielders and playmakers to have ever graced the game have been as slow as a sloth and have possessed zero ambidexterity.
Pace and the use of two feet is welcome in any position across a football pitch, but it's not the be all or end all for some players.
ERRORS WILL ALWAYS BE A PART OF HIS GAME
When you play such a high-risk game to yield rewards for the team, errors are always going to occur.
And the fact that Xhaka plays just in front of the back-four, a misplaced pass or a lapse in concentration will impact the team heavier - they have led to a number of goals.
It's something that, in a perfect world, the Swiss would abstain from, but to do so would be a complete rebrand of his playing style.
Sapping him of his risky passes would leave Arsenal with a player who only strokes the ball around simply, is unable to run and can't defend.
THE KEY MAN VS SPURS
After his rest in the 5-1 win over Bournemouth, Xhaka will re-enter the fray against Spurs ahead of Emery's most vital week yet as Arsenal boss.
A trip to Rennes next Thursday is followed by a home game against Manchester United.
Against Tottenham, Xhaka is the man that can help deliver Emery's first big away win and one that blows the race for Champions League football wide open.
The Gunners will have to sit compact to deal with Spurs' attacking threat, but on the rare occasions they have the ball, Xhaka's unique passing range will come into play.
Guendouzi and Torreira shined against an open Bournemouth side, with Arsenal enjoying the majority of the ball.
Against Spurs, that won't happen and Xhaka will need to be at the very top of his game if the Gunners are to snatch a victory at Wembley.
A year ago, few would have ever thought that the Swiss would be so vital in such a big game, but there's no getting around it, Arsenal need their £35m midfield general more than ever.