Chelsea fans could have been forgiven for wondering what all the fuss was about.
Here was a £30m Brazilian playmaker - a target for Liverpool and Tottenham - who spurned both for Stamford Bridge. A victory for Roman Abramovich, another midfield creator for Jose Mourinho.
But where would he fit in? After all, Willian found himself sitting next to Juan Mata, the club's reigning player of the year, on the bench.
Kevin de Bruyne was in, then quickly out. Andre Schurrle still looks an early favourite of Mourinho's, while Oscar and Eden Hazard have been first-choice since his arrival.
So, why spend upwards of £30m for a player whose primary position is so well stocked already?
Well, against Arsenal on Tuesday evening at the Emirates Stadium, Chelsea fans saw the first few lines of an answer. Because Willian is actually very, very good.
It's funny how quickly people can cast judgement - first impressions are everything at the highest level.
Willian was bitterly disappointing against Basle and Swindon Town and Mourinho left him on the bench for matches against Fulham and out of the squad entirely against Spurs.
How much of that could be attributed to his lack of preseason and his presence in the bizarre situation at Anzhi was not clear.
With so much competition, Willian had quickly fallen down to the bottom of a very talented pile.
A brief cameo against Norwich hinted at his key attributes. His 25-yard rocket into the top corner came out of nothing, he's a difference maker. But can he carve out a role in this packed Chelsea midfield?
Oscar is the link between midfield and attack, valued for his work ethic in a Chelsea team that Mourinho intends to press hard and counter quickly.
That's where Schurrle's value comes in as well - he's a tireless runner, quick, strong and technically proficient on the ball.
He's not as gifted a passer or dribbler as Juan Mata, but he's faster - and that works better in a system Mourinho has designed to work most efficiently at pace.
Hazard too is quick across the ground, and much more direct than de Bruyne.
So what about Willlian? Against Arsenal he was one of the hardest workers, constantly earning enthusiastic encouragement from the Chelsea boss on the near sideline as he worked back to help Ryan Bertrand effectively shackle Ryo Miyaichi's pace.
And going forward, he gave Carl Jenkinson a torrid time. The Brazilian flair was there, on more than one occasion he skipped past a Gunners defender with a little drop of the shoulder and a burst of acceleration.
He's quick, skilful and creative in the final third. He's not always the most careful in possession, but the back heels and tricks came off last night. That won't always be the case but Mourinho forgives those who track back.
His passes around the box opened up several opportunities for a Chelsea team that time and again streamed past Arsenal's midfield duo of Jack Wilshere and Aaron Ramsey.
One lay-off in particular, into the path of the on-rushing Michael Essien, deserved better than the woeful miscue it received. It was perfectly weighted. A Juan Mata pass from a Mourinho player.
The touches were there when they haven't been previously. They suggest Chelsea have a real player capable of making a telling impression on the title race.
Hazard and Oscar are Mourinho's two first-choice players in the attacking midfield positions at the moment. Hazard seems a lock, Oscar slightly more vulnerable.
So there's one place, possibly two, up for grabs as Mourinho looks to decide upon his best eleven.
De Bruyne received a hearty handshake from Mourinho upon his substitution but it seems unlikely to be the Belgian. Schurrle has started brightly, but if Willian can match the German's work rate, he can usurp his position in the team with superior skill.
As for Mata? Well, Mourinho learnt nothing new last night. The Spaniard scored an exceptional goal, was generally superb and tidy in possession.
But he can't break past players. On one occasion, he burst onto the ball as Chelsea broke forward into the Arsenal box, but the pace of the attack broke down as he received the pass.
He knew he couldn't match Laurent Koscielny for strength or pace, and he checked back out of the box. He kept hold of the ball, but the dynamism was lost.
That's what Schurrle and Willian can offer. Up to now Schurrle has been the man - that's why Willian found himself playing with the Chelsea B team while the German had his feet up.
But for the first time Willian looks like a real contender. Because last night, he looked like a £30m player.
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