He has the strokes. Here's how I came to my rating of 4.5+, the OP asked to rate the player on the far-side, that's what I did. I paid NO attention to the player in the sweats--no offense to him--but he must be an excellent player to be on the same court and wearing sweats. Tennis is about timing, footwork and technique--the player I was asked to evaluate has all three. He has a full range of motion on all his shots. He has excellent technique, he has excellent timing, he has excellent footwork. He is very fit, not carrying any extra weight! Fitness wise, he's in better shape then many WTA players. He comes to the net on short balls and has correct volley technique-he's an all court player.
He is very flexible, loose and confident on the court. He's wearing a short sleeve shirt so he Nadal is probably one of his role models. We didn't see any serves--which is the MOST important shot in tennis. If he has a serve to match the rest of his game, then he's easily a strong 4.0 in a very competive region, NORCAL--home to Don Budge, who some who knew him, say he could have been the greatest player in history, and certainly in the top ten, and having the "best BH" in history. Also Tom Brown and Whitney Reed hailed from his part of the Bay Area. Can't discern his age from the vid but he could be in the top ten in his age group locally and since he's from kali top ten nationally. The vid does not measure heart or the choke factor, but I bet he's very competitive and doesn't give up on matches, he can come from behind if he has to and wins his tie-breaks.