Interesting. I can instantly recognise a player/number combo on the field - but the number itself only, I have some trouble with. I missed a few obvious ones, and was reduced to naming players and then saying 'Of course! he was No ###!' when it popped up. I had huge trouble remembering who the current No 23 was - despite the fact I've seen him play so many games.
I also think the modern system of not having set positions makes it harder to remember sides. 'Full Forward, Resting rover, resting ruck, CHF, flanker, flanker, etc' , .......used to be a lot easier than '7-8 mids, 1 tagger, 2 tall KPFs, 3rd tall (or did we go small this week), sweeper, swingman etc..........'.
230s somewhere.