A very decent performance against Chelsea, yeah, I consider that "some sort of potential", which is the criteria you gave. I'm not saying he's the next big thing, mind, but there's something there.
I watched the game and I can't say he stood out for me. Frei certainly did but to hand I can't recall anything Sa did particularly well. This was against Chelsea's reserves also.
I've been to the Emirates a few times and it is decent. As is the Bridge for the big games as well. Sadly unless it's a night game or Arsenal, Spurs, Man U, City etc the Bridge tends to often be subdued. I suspect the Early kick off can't have helped either, many would have had at least 11am starts the day after Christmas