Thiago Alcantara's arrival at Liverpool has given Jurgen Klopp the cliched, theoretical headache that every manager wants.
Jordan Henderson. Georginio Wijnaldum. Naby Keita. James Milner. Alex Oxlade-Chamberlain. Curtis Jones. Fabinho. And now Thiago.
With those eight players vying for three spots in the team, the German faces an uphill battle to keep everybody onside. Among the floated potential solutions, however, the idea of playing Fabinho in central defence was one of the more theoretical.
He had played there before, but sparsely, and only when absolutely necessary. Prior to Saturday, you have to go back to February 2019, when he partnered Joel Matip against Bayern Munich at Anfield, for his last start at centre-back.
After 90 minutes at Stamford Bridge, however, it's something we may see a little more often.
Any concerns we had about how he would cope with the counter-attack were immediately put to bed. Though he seemed positionally erratic, it became clear after a while that this was the point. He had been asked to be tenacious, step out, and nip attacks in the bud before they start.
Kai Havertz, playing as a false nine in an attempt to catch Liverpool out, looked apprehensive to take a touch at times, in fear that a baying Fabinho would soon be at his heels. Timo Werner may have foamed at the prospect of playing up against such an aggressive defender, but he was unable to take advantage of the space left behind by the Brazilian, because he so rarely got there.
Fabinho finished the game with more tackles and interceptions than anyone else on the pitch (8 combined), and showed why injuries to Joe Gomez and Joel Matip are no longer the disaster they might once have been.
He remains Liverpool's best defensive midfielder, but Thiago means that there are now two viable alternatives for the 'six'. Thiago's own performance, in which he completed more passes after coming on at half-time than any other player has in 45 minutes of a Premier League game since records began, hinted that me may now be the player to take on that role going forward.
But if that's the case, then it should be welcomed with open arms. It's a system formed by necessity, but Fabinho's raking distribution from the back, masked by the tidy and incisive Thiago, only adds to the Reds' ability to unpick defences from any position.
The 'back five', in this set-up, would feature five of the best passers in English football.
Fabinho's emergence as a central defensive option not only creates possibilities in possession, but alleviates the need for another dip into the transfer market. Liverpool will need to sell to justify the surprisingly substantial business they have already done this summer - close to £80m has been put down on Thiago, Kostas Tsimikas and Diogo Jota - so they could do without having to sign a replacement for Dejan Lovren.
Three senior centre-backs is not enough to get by on. Three senior centre-backs and a midfielder who won't cower at a prolonged run in defence? You'd say that probably is.
It had previously seemed as if Fabinho's role in the Liverpool team was cast in iron. He was the defensive midfielder, and that was it. But roles change over time.
He may find himself gradually morphing into Klopp's modern-day utility man, setting the standard both in defence and midfield, but as long as he plays both roles as diligently and capably as he has until now, then his manager will relish having no clue where to fit him in.