With the current dearth of top-class fullbacks (it's not that there aren't, there just are very few truly world-class players at the moment), I'd say Ivanovic is one of the very best RBs around right now. Anyone we sign (especially because there are only maybe 3-4, if that, better RBs) is gonna be a back-up. That includes Azpilicueta, Maicon, Debuchy and anyone else we've been linked with.
When we sign Azpi (and I say when because if we don't sign him or someone similar I will kill someone), he will be 2nd choice. He'll get games, of course, since Ivanovic is also our 4th choice CB (and he's 4th choice because he's 1st choice RB, if he was only a CB I'd consider him a starter), and Azpilicueta offers more width and drive going forward. He'll get plenty of games against lesser opposition. That's why Azpi is perfect, he's young, he offers something at RB that Ivanovic doesn't and won't demand high wages or too many appearances, which Debuchy might. Not to mention that Debuchy is reaching the peak of his career which means we'll be looking at losing both our RBs in the space of a 1-2 seasons.
Either Azpilicueta now or Maicon now and re-evaluate the market next season, but we need someone quick.
Also, Terry will only miss the Supercup, and not the first CL match too, and Ivanovic sounds like he won't get a ban because the Shield is considered a friendly.