It’s not a fair comparison. Facing a bunch of league two players many of whom won’t have taken a penalty for years if ever if absolutely not the same as facing PL’s first choice penalty taker who will have been practicing the penalty all week. It’s absolutely night a day. Plus Sanchez saved his last but one penalty in the PL.I think its still a fair comparison. In front of a penalty spot the difference between a League Two player and a Premier League player isn't massive.
Think its a confidence issue: when you've let 10+ penalties in in a row, you're going to be insecure in that situation. Once he has a bit of luck and manages to save one, I think it will be first of many penalty saves.