Sounds like you enjoyed the experience, I hope so. I suspect your experience in both Basketball and baseball taught you a lot of people EXPECT you to know everything IMMEDIATELY, and you've learned knowing what you need takes time (and mistakes). There's no alternative to learning the rules, which ONLY happens over time.
As best you can, focus and learn the position you're assigned to, and as much as possible observe what your crew mates do to handle their position. 3 man assignments worked fairly well 40+ years ago, but the game has changed dramatically since then (at any level). Although you're working with 3, spectators, and many coaches, will hold you responsible for seeing everything the 7 or 8 men see on TV. Like basketball and baseball, that's just part of the gig, and your diplomatic experience should serve you well.
3 man mechanics is exactly like driving a car with 3 wheels, it's possible but usually very bumpy. R-U-L is the traditional formation, but many have switched to R-L-J, to compensate for that previously open sideline in today's wider game. It's still only 3 wheels no matter where you place them.
Don't be impatient, focus on the game and the more snaps you see, the slower things seem and the more detail you'll be able to see. Hang on, it's a great ride that only gets better.