Yep - agree with all thatSaka is exceptional for a 20 year old - an absolute dream player for any coach.
It's not just about his output in terms of goals and assists - it's the amount of tactical flex he gives you in a single player without having to make any changes. You need someone to create, he can do that. You need goals, he can do that. You need someone to dribble, he can do that. You need someone to drop into midfield and transition the play, he can do that. You need someone on the left / right / centre - he's got it covered. You need someone to fill in as an 8 in midfield - Saka. You need an emergency LB - Saka. He attacks and defends and does any and every job he's asked to do equally well, and he does it with a fantastic attitude.
Again, this kid is 20 - 20 years old! Give him another 2 or 3 years and, as others have said, put the right support around him (some strong, direct competition so he can occasionally have a rest, a decent striker to finish the chances he creates, a squad with more depth so he doesn't have to keep filling in everywhere, etc) and he'll develop into one of the strongest players in the league.