Here is a question from Alfredo in Florida. â€œIt is generally recommended for practicing your ball toss to place a racquet or a bucket slightly in front of your left foot and toss the ball so it will fall in the bucket or the racquet, whichever is used. Something that puzzles me is that some of the pros with the best serves toss the ball such that the ball describes a â€œbowâ€� like trajectory. They release the ball as recommended but the ball, if let fall on the court would fall about 1.5 - 2 feet to the left of the racquet or bucket placed in front of the left foot. Good examples of this are Pete Sampras and Marat Safin. I saw a USTA satellite tournament where a guy with a great first serve took this to an extreme. He would toss-release the ball with his arm almost paralell to the baseline and would actually hit it nowhere near where I would place a bucket or a racquet on the floor, but way to the left. It looked like he hit it to the left of his head in front of him. He had a trememdous pace and very good control.â€œ
The service ball toss that goes straight up and comes straight down is for beginners. Beginners use a eastern grip to serve so this ball toss placement is perfect for them. Beginners don't use much shoulder rotation so there is no need to bring the toss arm back. The pro's however are using a continental grip to serve. This means their ball toss must be slightly to the left as you mentioned. The reason for the "bowed" toss as you described is because players must turn their shoulders 15% away from the net to achieve a good shoulder rotation. This makes it very difficult to turn your shoulders while tossing with the arm in front towards the net. Most players do bring the toss arm back with them on their ball toss and shoulder rotation. I do teach my advanced players to bring the toss arm back almost parallel to the baseline like you observed. This allows the player to toss the ball in an arc over the left shoulder (for right handers) and still be able to have the ball toss end up inside the court.