As you well know, it's a question of matchups.
The majority of juniors play a strong hitting baseline game, from both wings, have superior speed, and excellent endurance. Most, not all, have somewhat weak serves for their tennis ability.
Adults often are out of shape, might slice more on backhands, usually have much better net play (talking 5.0, or A/Open levels), have played more top players than any junior has seen, serves bigger, uses smarter tactics, but don't nearly match up in baseline bashing consistency skills.
So, which adult 5.0 is facing the top junior today?
Which junior is facing the 5.0 men's player, who can serve into the 130's, and run like TonLars?
And throw in the lefty angle, either side. And how wisely they serve?
As we all know, a 5.0 player can beat one top level junior, then lose bagels to another.
As we all know, a top junior can beat one top level Men's 5.0, and lose bagels to another.