Taking my own stab at this: Almost everything in Shelton's game is still projectable for further improvement (serve placement, groundstroke rally tolerance, volley consistency among others). He probably wasn't top 20 quality when his ranking first landed there on his slam runs, but he's 19-10 (65%) this year on the tour and that is about right for a top 20 player.
His return game is bad and that's quite concerning because that doesn't often improve significantly with time, but there is a silver lining in that he's one of the best in the game at not getting aced despite not having as egregious a deep return position as some of the other people atop that list (Medvedev). He also misses a lot more second serve returns than most players. So maybe he's got some athletic tools that can be refined as we play against years of professional level servers and their speeds/spins.
A decent progression path leads to Taylor Fritz/John Isner, where we hang around the back of the top 10 or just outside for a while and maybe sneak a Masters or two. That takes a 65-70% winrate.
A good progression path is probably the Raonic/Tsonga mentioned above, or for a clay-loving but still big serving profile Tsitsipas (Top 5 at times, a sizable collection of slam quarters and better), which takes probably 70-75% winrates.
An amazing progression probably doesn't get us any better than Andy Roddick because of some key limitations. But even being about as good as Andy Roddick (~75% career, 80% peak season WR) would be an enormous deal for American tennis. It's a long, long way off though, and relies a lot on our serve going nuclear and taking our current ~86% game hold ratio up to more like 93% and becoming the best server of his generation and one of the best of all time.
His return game is bad and that's quite concerning because that doesn't often improve significantly with time, but there is a silver lining in that he's one of the best in the game at not getting aced despite not having as egregious a deep return position as some of the other people atop that list (Medvedev). He also misses a lot more second serve returns than most players. So maybe he's got some athletic tools that can be refined as we play against years of professional level servers and their speeds/spins.
A decent progression path leads to Taylor Fritz/John Isner, where we hang around the back of the top 10 or just outside for a while and maybe sneak a Masters or two. That takes a 65-70% winrate.
A good progression path is probably the Raonic/Tsonga mentioned above, or for a clay-loving but still big serving profile Tsitsipas (Top 5 at times, a sizable collection of slam quarters and better), which takes probably 70-75% winrates.
An amazing progression probably doesn't get us any better than Andy Roddick because of some key limitations. But even being about as good as Andy Roddick (~75% career, 80% peak season WR) would be an enormous deal for American tennis. It's a long, long way off though, and relies a lot on our serve going nuclear and taking our current ~86% game hold ratio up to more like 93% and becoming the best server of his generation and one of the best of all time.
