One big mistake by Sanchez and Wanyama is the difference in the game. Arsenal have the lead but I don't think on balance they've been the better team. It's been pretty even, I think.
I've been right that Spurs can't build through midfield and have no buildup other than through Trippier but that's been mostly ok because Arsenal are not marking Trippier and Trippier is playing pretty well. He is constantly getting into space and playing dangerous balls into the box. And because he's always open as an out ball and Spurs have centerbacks who can hit accurate long passes, he's disrupting Arsenal's press. Emery's plan to leave him open is not really working.
When Arsenal do mark Trippier tight Spurs can barely play out of their own half. But that requires the whole back line sliding across and pushing higher and that makes them more vulnerable to Kane and Son running in behind (which is how Spurs beat them at the Emirates in December). I wonder if we'll see some adjustments and counter-adjustments in the second half.
Wanyama has looked rusty, and while has passing hasn't been good his pairing with Sissoko has a lot of physicality and except for the one obvious example they've been good at breaking up Arsenal attacks.