The Blues had a busy deadline day as they confirmed the late signings of the Brazilian centre-back and the Spanish left-back, and Antonio Conte will now be pondering how to fit them into his new-look side.
Chelsea have mainly played something between 4-2-3-1 and 4-1-4-1 under Conte so far, but could the addition of Luiz tempt the Italian into trying out a move to three at the back?
This system worked well for Conte during his time at Juventus, and may also be the best way of utilising the strengths of the eccentric South American, who wasn’t seen as the most reliable defender in the world during his first spell at Stamford Bridge.
Here’s a look at four ways Chelsea could line up after their deadline day deals…
First up, Chelsea could continue as they are with a 4-2-3-1, but replace the ageing John Terry with Luiz as Gary Cahill’s main defensive partner.
Conte has made no secret of his desire to sign a new defender this summer, and Luiz will surely be coming in to be first choice with the kind of money the Blues have spent to bring him back to the Bridge.
Meanwhile, Alonso will likely be a first-team regular as well after a £23million move from Fiorentina, which could mean replacing Cesar Azpilicueta at left-back as one option.
Alternatively, Chelsea could try a 3-4-3 formation that looks something like this line up above, with the personnel largely the same, but with a few tactical tweaks.
With Branislav Ivanovic capable of playing centrally, he could move into being part of a back three alongside Cahill and Luiz, which would take the pressure off the Brazilian to be one of the main men at the back, allowing him more freedom to move forward, as we all know he likes to do.
This would then likely see Alonso in a more advanced wing-back role, and would also allow Cesar Azpilicueta back into the side as a right-sided wing-back, though that doesn’t necessarily seem the most sensible way of getting the best out of the defensively solid, but relatively unadventurous Spaniard.
Another way Chelsea could line up with three at the back is in more of a 3-5-2 formation, similar to that used by Conte’s Juventus sides.
Ivanovic would again likely feature centrally, and new signing Alonso is also capable of playing there, so could slot in on the left-hand side of the back three.
This line up also allows for more playing time for fellow summer arrival Michy Batshuayi, who could take the pressure off Diego Costa to be the main goalscorer by partnering the Spain international up front.
Finally, could Luiz even be used in midfield by Chelsea?
The 29-year-old has played there in the past, though not with a huge amount of success, but could Conte try to make it work in a line up like this?
Despite signing N’Golo Kante, the Blues have also been heavily linked with more signings in midfield this summer, and it could be that they will now favour the inclusion of Luiz in that position instead of the slightly off-form Nemanja Matic.
As for the back four, this could give more of a chance for Terry to keep playing regularly, with Alonso also perhaps kept as a backup option to start off with as Azpilicueta and Ivanovic remain in the same full-back roles.