Irreplaceable?.. oh, come on!
He's flitted in and out of form this season; in fairness, his last game against West Ham I thought was his best this season. Bamba has had a more positive impact on our games than Gunnarsson and has been more of an unelected captain than Gunnarsson in my opinion, more vocal and encouraging.
I will wish Gunnarsson well, but I would like us to find a midfielder with better passing ability than him, that way we might retain possession a bit better.