Well I'm going to be the contrarian here. Yaya is one of my all time fav City players and I don't believe he's 'lazy', his legs can only do so much.
But IMO it's a mistake if we keep him and it's short-term thinking instead of long-term strategy (hey, that pretty much describes our transfer strategy in the last few years). There are ALWAYS replacements out there. Sometimes you need to buy two players and rebalance the midfield, but there is always a way. This is our last chance ever to get a decent fee for Yaya and it + the freed wages could be used on some excellent emerging midfielders.
The 'we can't afford to sell [ageing veteran]' argument is a sentimental one IMO and ignores that there are brilliant midfielders out there who may not be as unique as Yaya but could possibly bring other things like the hard pressing we're fatally lacking in European games.