I posted this a while back:
If anything, my opinion has only strengthened, having seen the improvement he made in one game without Martinez. There were whispers that we worked on set pieces for the first time in months and obviously Stones was told "play your way, but if you're in trouble, row Z please."
You could also see it when he played for England. Despite what the media hate brigade made note of, Stones had a great game. He was composed, keeping the ball when he could, but made no mistake of getting rid when needed. He also made some important tackles. But the media would rather focus on a single backpass which appeared risky (which Hart had no trouble getting to) than all the positive points of his game, or Cahill's lack of doing anything, or Hart's inability to catch, or Kane being unable to kick a dead ball.
If I had a choice between keeping Lukaku or Stones, I'd keep Stones without a second thought. The club has to do everything they can to hold on to him.