He has the ability, but he doesn't have the desire or mental strength to sustain high level performances. To be a top player you need both of these traits, so I think he needs replacing.
Unfortunately though, he's just one part of the perfect shit storm this season. We were lacking a striker, some pace, a left back, a right back and a creative DM.
Tosun and Walcott should help with the first two, and Coleman is on his way back. 3 down 2 to go, and then we have our balance back.