Honestly, Higuain offers something that Dybala will never be able to offer as a 9. He can hold the ball with his back to the goal, and distribute to the wings. If that's what Sarri's looking for in his striker Higuain will be a starter for a good portion of this season. The only thing Dybala can do is work his but off when he comes on and prove he can contribute in a different way as a striker, and do it for a consistent basis to convince Sarri that way.