And let's not pretend Smalling wasn't solely responsible for the third goal. Shocking defending to let Obertan (of all people) in from a throw in. Along with De Gea the biggest personal mistake from all our defenders today.
What I'm saying is defenders will make mistakes. If your team is not organized enough to cover for players occasionally making mistakes then you're gonna let in goals.
If your defenders aren't playing well enough to cover for other players making mistakes, and are vulnerable due to the rest of the team being poorly organized/set up (no midfield) then this season happens.
I don't think Vidic and Rio in their primes would have relished having Gareth Bale running at them one v one centrally because we have no midfield. And it's difficult to stop a goal when an opposition winger is allowed to burst unchallenged into the box full pelt while players are arriving behind your back.
Having said that, Evans has played poorly at times this season, notably these last couple of matches. He's still been our best defender except for Rafael.