If we are getting a younger CB, then here is a few worth looking at;
Mateo Musacchio, Kyriakos Papadopoulos and Dede, all young and promising and would n't cost the earth in transfer fee or wages. Another one worth looking at is Mathias Jørgensen, although he has just joined PSV on a free transfer so we will have to leave him be for now and may be go in for him in a few transfer windows time. Any one of the top 3 would do, we get a young CB who could develop in to a world class player and a stalwart in our team, and we don't break the bank. A loan for Savic, and Boyata as 4th or 5th choice depending on how RekiK does. If one of our backups suffers for form put Micah at CB, if we get rodriguez as a winger or WB then we won't be left short at fullback. Although Kolarov has been linked with a move away so maybe get Radu as a replacement for Kolo and Kola.
How about this as a defence this season;
Richards, Kompany, Lescott, Clichy, Zaba, Matias Rodriguez, Boyata and Radu. They should all get enough games as Zaba and Radu can fill in at LB and MR can play further up the pitch as a winger, and RekiK though young may break through this season in which case we may move on savic and Boyata next summer.