Let's start with the Chelsea news. Oriol Romeu hasn't featured in forever and the minor injury that's been bothering him has apparently forced him out once more. Not a big deal, that, although it answers the questions about just where the young midfielder is. John Terry's injury is a different matter entirely.
The captain was rushed back from a knee surgery and forced out of the match against Napoli during extra time, didn't feature in the 5-2 win against Leicester City and now is going to 'probably' (update: certainly) miss one of the most difficult games of the season. He's expected to be back for the Tottenham Hotspur match this weekend, although I wouldn't hold my breath on that one. Fortunately, David Luiz and Gary Cahill form a reasonable defensive partnership even without Terry around.
As noted by David McDonnell, City have injury problems of their own. If both Vincent Kompany and Joleon Lescott are missing, Roberto Mancini and friends are going to be in very deep trouble. City don't have very good depth at centre back, and deputy defender Stefan Savic has been very, very poor whenever he's been fielded. Hopefully Chelsea can exploit the gaps that'll appear in the back, while minimising the damage that the home side's strikers can do to our back line.