What you have to also consider, Williams would have done zero match preparation for this game for playing right back. Literally not one bit of training this week with that in mind. Then 10 minutes before kick off, due to unforeseen circumstances he gets thrown in there and asked to do the job. I thought he was fantastic. He got caught out positionally a couple of times in the first 15 minutes, which was to be expected - of course he's going to naturally gravitate higher up the pitch. But thereafter he did not put a foot wrong. What I like about him is that he is a bit more tenacious and aggressive than your typical winger and seems to enjoy getting stuck in a bit, which perhaps lends itself well to doing a fill-in job at RB.
It's also a great goal by him as well when you look at it in its entirety - he dispossesses their player on the edge of our box, plays it to Brannagan and then just does not stop running, sprinting a full 60/70 yards and doing what all good players do and following up the shot. Ok the finish may be a sidefoot from 6 yards, but its just desserts for his work at the other end of the pitch.