When I was relatively new to the game, I used to watch the warmups,
trying to see who looked sharp and who didn't. While I didn't
keep stats on it, it seemed to me that the guys who looked sharp
in the warmups didn't win any more often than could be expected
through random distribution, so I stopped paying attention to
the warmups.
Maybe you could spot something in the warmups, like a guy having
trouble with his cesta, but overall I don't place any importance
on what a player does in the warmups. I prefer to watch what he
does in the games.