What do posts 1 and 2 tell us?
The first point of the game is unique - it always has the same two posts, in the same position. So, we know that 1 and 2 should be mirror images in the statistics, since one will always win and the other will sit down.
What can we learn from this?
On average, #1 will serve 1 more time per game than #2. So,
by separating singles and doubles games, we can compute the relative
advantage of serving/receiving in singles/doubles, by looking
at the relative performance of #1 and #2 teams (after correcting
for player ratings, of course). The same applies, to a rapidly
decreasing extent, to #3, #4, etc.
By studying a player's performance in post 1 (let's say in singles) and comparing against ALL post 1 performances, we can also measure the relative effectiveness of his serve.
OK, guys, what else can we deduce from this unique situation?