Why don tennis pros use the ball in their pocket after a 1st serve let?
It’s so that they still have a backup ball if they fault on the second first serve. Here’s the scenario: Server takes two balls at the start of the point. One is put in his/her pocket. The other is used for the first serve. First serve is a let. Currently, the server just has the one ball from his/her pocket left. If the server were to just use that one, and then fault, he’d have to stop and get another ball for the second serve. This might not seem like a big deal, but it’s poor etiquette in tennis to have this kind of pause between a first and second serve. It’s likely to throw off both the server and returner. So they always make sure to have two balls on their person before any first serve. EDIT: Look at it this way. If you consider the first serve as the start of the point (whether it goes in or not), then messing around with getting another ball is like causing a delay in the middle of the point. That’s the best way I can really describe it. There’s a flow that exists between a f
