Balance means a lot for any football club. Without it, success isn't always forthcoming.
Above all, though, Willian's industry is the one quality Jose Mourinho will admire most.
It can sometimes take the focus away from the Brazilian that he is actually a gifted footballer, possessing his own skills and tricks, yet his work rate for this Chelsea team is outstanding.
Throughout pre-season, Mourinho has shown the tactical tweaks he has made since the end of 2013/14.
Chelsea have played a higher line in attack, pressuring the opposition in their own half and, at times, squeezing them back into their penalty area as they chase possession.
Early in the campaign, it was his younger players on hand to put that plan in action, but it's one the seniors will have to make successful if Chelsea are to lift trophies this year.
Willian will be a big part of that.
It's very un-Brazilian, but then Willian has never quite fit the mould of the Samba Boy stereotype.
His journey to Chelsea wasn't via the glamour of Spain, Italy or Portugal—the path often travelled by his compatriots. No, he arrived at Stamford Bridge on the back of playing in the industrious heartlands of Ukraine for six years before a short stint in Russia.
His education with Shakhtar Donetsk has stripped him back and what we see now is a player who puts in the hard yards, works for his teammates and forms a key part of Mourinho's dynamic.
It isn't just about running where Willian is concerned, though; it's how effective he is at closing down space, finding himself in the right positions and knowing when to attack or pass.
Mourinho teams have always been about that industrious quality. Every player has to work hard before they earn the right to display their more eye-catching abilities.
Even when Frank Lampard was scoring 20-plus goals a season, his work rate at the heart of midfield was just as important to the success Chelsea enjoyed.
Mourinho needs players like Willian.
For a man who cost £30 million, you wouldn't know it. There isn't an ego with the 26-year-old, no demands being made that set him apart.
He is at Chelsea for the team, and without him, there were times when the Blues struggled last year.
Nemanja Matic made an incredible impact further back in midfield when he returned to west London in January. Chelsea started to control games more, breaking up play and numbing the threat of the opposition.
We need only ask Manchester City about that fact.
It was no coincidence that at the same time Willian was coming into his own, too. After a few months of bedding in, we began to see why Mourinho was so eager to steal him from under the nose of Tottenham Hotspur.
That move had been dressed up as him getting one over on his former apprentice Andre Villas-Boas, but as the season developed, the perspective changed.
Chelsea had got a real player.
A year on and with Mourinho's team more like what we expect from him, Willian's style will be a key component to the manager's plans being implemented in 2014/15.
We can talk about the qualities of his teammates, but when Chelsea step out at Turf Moor to face Burnley on the first step to reclaiming the Premier League trophy, it will be the more subtle attributes of Willian that will give them the platform.
Garry Hayes is Bleacher Report's lead Chelsea correspondent. Follow him on Twitter @garryhayes