I don't think you should or will sell him either. Squad players are important, and you need depth to compete for the title, so Coquelin is definitely more valuable than £10m in that sense. But then again it's Wenger who seemingly has lost the plot. If you guys lose Sanchez, Özil, Coquelin and more, then I wish you guys a lot of luck, since that season will probably be reminiscent of Moyes' first season for Manchester United.