I don't think comparing Traore to Costa is a fair example, as Traore was always the focal point of Boro's attacks whereas Costa was never the focal point last season and played about 820 less minutes than Traore did, that's more than 9 games. In that time Costa got 5 goals, 6 assists to Traore's 5 goals, 10 assists. 2016/17 where Costa was the focal point - 10 goals, 8 assists, and only about 170 more minutes so just under 2 games and playing in a much weaker team.
This season Cav got 9 goals, 12 assists with about 150 mins more, which is significantly better than Traore despite, again, not being the focal point of our attacks.
I do like to come out with the 'faith in Nuno' line but the thing is, most of our signings have been players I have had no clue about anyway. I'd heard of Ruben Neves and Diogo Jota but don't think I ever saw Neves, and only saw Jota once in Porto's thrashing of Leicester's reserves where he did pretty well to be fair. But players like Vinagre, Boly, Bonatini, Douglas - I knew nothing about them. They all turned out to be good signings, so he has earned what I could call blind faith in the players I don't know anything about.
But players like Ruddy, Bennett, N'Diaye, Afobe, the ones I did know about, you can only say that he improved Bennett while the rest just matched the expectations we had. Most people thought Ruddy would be an upgrade on Ikeme and he was, but he was never tested often enough to see how good he really was. N'Diaye was average at Sunderland and pretty hit and miss at Hull - he had a few stormers like his debut against Liverpool but at other times wasn't good enough. He was fine for this level but can't say I saw him get any better during his time here and it was quite clear we needed better for the Prem so off he went. Everyone knew Afobe could score goals at this level and he can, but he just didn't fit the style of play. I'm guilty of thinking Bennett was a more rubbish Danny Batth so I'll hold my hands up on that one, improved massively and got rid of his habit of hoofing the ball away. Improved a lot on the ball and doesn't feel like he has a massive mistake in him just waiting to happen any more. I think he has earned his chance in the Prem and am not going to lose my mind if he is starting against Everton.
What I am basically saying there in long-winded fashion is that of the players he has signed, the ones I knew nothing about have turned out to be good for the most part so I'm happy to put my faith in Nuno and the scouting team to have found a good player. But the players that I did know about have, save for one, been like expected. And I don't think Traore will be that good.
That isn't me criticising Nuno, just saying that what I have seen of Traore with my own eyes is overriding my willingness to put blind faith in Nuno.