We need better full backs. Zabaleta is very good, but offensively he is isn't as fluent or creative as he could be. Clichy is normally solid and relaible, but again doesn't offer anything in the final third. Kolarov does, but he isn't very mobile nor fluent with the ball.
We need another centre half to replace Lescott, although i wouldn't be too bothered if we just allowed Rekik to come back and play. He's been good this season for PSV. Nastasic is to come back yet, and MDM has been very good over the last couple of months, now he has settled down.
Other than that, probably someone in midfield who can challenge Yaya and Fernandinho, or compliment them. He needs to be fluent on the ball.
Our main problem is that we have maybe 6 or 7 players on the pitch who are fluent and quick with the ball, whereas the top teams in Europe have 10 or 11. This is the level we aspire to and to get there, we might have to see less of some of the players we love, which means that guys like Zabaleta might end up merely becoming squad players.....which would be sad to see as everyone loves him, and rightly so, he's a hero.