here's a (non-exhaustive) list of defenders signed by big clubs in the past 3 seasons. Play hindsight Txiki and pick yours, you have roughly what we spent on our defence which let's call it £110m to play with.
CBs
Nicolas Otamendi MCFC £28.5m
Eliaquim Mangala MCFC £32m
John Stones MCFC £47m
David Luiz CHE £34m
Michael Hector CHE £4.5m
Papy Djilobodji CHE £2.5m
Gabriel ARS £12.75m
Shkodran Mustafi ARS £35m
Rob Holding ARS £2.5m
Dejan Lovren LIV £21m
Joe Gomez LIV £4m
Ragnar Klavan LIV £4m
Joel Matip LIV Free
Daley Blind MU £14m
Eric Bailly MU £30m
Eric Dier TH £4.25m
Federico Fazio TH £8m
Toby Alderweireld TH £13.5m
Kevin Wimmer TH £5m
Jeremy Mathieu BAR £17m
Thomas Vermaelen BAR £16m
Samuel Umtiti BAR £21m
Jesus Vallejo RM £4.25m
Stefan Savic AM £21m
Daniele Rugani JUV £4.25m
Medhi Benatia BM £23m
Mats Hummels BM £29m
Matthias Ginter DOR £8.5m
Marc Bartra DOR £7m
FBs
Filipe Luis AM £13.5m
Kenedy CHE £7m
Abdul Rahman Baba CHE £17m
Marcos Alonso CHE £19m
Alberto Moreno LIV £15m
Luke Shaw MU £27m
Marcos Rojo MU £17m
Ben Davies TH £10.75m
Lucas Digne BAR £14m
Guilherme Siquiera AM £8.5m
Patrice Evra JUV £1m
Alex Sandro JUV £22m
Juan Bernat BM £8.5m
Raphael Guerreiro DOR £10.5m
Joo-Ho Park DOR £2.5m
Layvin Kurzawa PSG £21m
Ok, so I'm giving you £110m, go spend it in that transfer market. No arguing over prices. You already have Kolarov/Clichy/Zabaleta/Sagna/Kompany/Demichelis in your squad.
So go play hindsight Txiki, if it's popular I'll extend it to other areas of the pitch.