In last night’s Coupe Rogers match between Milos Raonic and Juan Martin del Potro, one point stands out from the rest.

Raonic won the first set, then Delpo broke early in the second. With del Potro serving at 4-3, Raonic earned a break point with a winner at the net. Replays clearly show that he touched the net. Had the chair umpire seen it in real time, Delpo would have been awarded the point.

The Argentine never recovered, losing the next nine points and the match.

The net touch, and the point Milos didn’t deserve, was clearly a turning point in the match. But how important was it, really?

If we assume that the two men were equal and that both players win 75% of service points (not true in Delpo’s case yesterday, but reasonable for two big servers on hard courts), here is a summary of Raonic’s probability of winning at various stages of the match:

- After winning the first set:
**75.0%** - With Delpo serving 4-3, 00-00:
**52.4%** - With Delpo serving 4-3, 40-40:
**53.9%** - After winning the “touch” point:
**58.9%** *If Delpo had won that point:**51.8%*- After winning the “touch” game:
**75.0%** - After holding serve for 5-4:
**76.3%**

The controversial point was, clearly, very important. The difference between winning it and losing it was 7%, a magnitude that doesn’t happen very often in a tennis match, especially outside of tiebreaks.

But the real story here is the *next* point. Remember that under normal circumstances, del Potro is a huge server and Raonic does not have a strong return of serve. (I say “normal circumstances” because somehow, Raonic won 50% of return points in this match.)

If a server is winning 75% of points on his own racquet, his probability of winning a game from break point down is still 67.5%. There’s a 25% chance he’ll lose the game on the next point, of course, but a 75% chance he’ll get back to deuce, where his serve gives him a 90% chance of winning the game.

The touch point increased Raonic’s chances of winning from 53.9% to 58.9%. The next point upped his odds from 58.9% to *75.0%*. Which one do you think was more important?

Another way of looking at this to consider what would’ve happened had there been no video replay, and no chance of del Potro spotting the touch and arguing with the umpire about it. Normal Delpo would’ve stepped back to the line and hit a service winner. Five minutes later he would’ve held serve again and the two men would’ve played a third set.

It’s easy to look back at this match and conclude that the net touch was the difference in the match. But no: It was the *reaction* to the touch–the controversy itself–that had a much greater impact.

Your statistical arguments look impeccable. But there was no question of Delpo hitting a service winner at any point in the match, because of his sore back/shoulder (there’s been no clear diagnosis). What I take away from the match is that, if Raonic and Delpo were to play when both were reasonably fit, Delpo would win fairly easily. That’s based on the observation that he nearly managed to make a match of it when his serve was a pale imitation of its normal self – and I imagine his ground strokes and his running were also constrained.

Jeff – How do Raonic’s odds get to 75% at 4-4 after the touch point? And why are Delpo’s so low when he starts to serve at 4-5?

R

Remember Raonic had won the first set. So the best Delpo could do at that point is even the match.

Assuming the players are even, at 4-4, Delpo has a 50% chance of winning the second set, and a 50% chance of winning the third. He needs to do both to win the match. Raonic only needs to do one of the two.

Jeff, would love a similar technical assessment of Djokovic’s net touch in the 5th set of the French open semi against Rafa. 🙂