Douglas Costa definitely has talent and skill to shine. I've seen some Shakhtar games and he has been very impressive. He's quick, very good on shots, and a very creative player.
United wanted to sign him when he's playing here, but Gremio asked £20M in that time. Quando o Shakhtar tried to sign him, they asked £7M. And he was sold by £6.5M.
He is an attacking midfielder, so I don't if he'd be exactaly suitable to the English style of play. But he'sa player with a great future. He'll be in Brazilian NT soon. That's a sure thing.
However, he need to change some attitudes. When he arrived at Shakhtar, he said it was a matter of time until he plays in a bigger club. In other words, He considered Shakhtar a stepping stone.