Sometimes, it takes a long explanation to a particularly obstanent fellow to explain why things aren't always as they seem. One cannot always assume that a 4.0 is a newbie tennis player with 4 years total tennis experience. A handful of guys I play with, or against, weekly, were former A/Open level player's. Those guys played pro tour events, even winning a few, but have gotten old enough they can't run for 3 sets against tough opponent's. That's why they're 4.0 now.
You might ask, why does a player lose his ability? From age.
Consider this. My SECOND year of tennis, 1976, I was asked to join in on some weekly doubles at Golden Gate Park. The guy who asked me was Art Larsen, who won some pro tennis event back in the '50's, maybe USOpen? Look him up. One of the guys in the doubles group was George Ponticoff, who won a SF City Open event around that time. The 3rd was John Murio, who won the SF City tournament, OPEN class, a dozen year's previous. That's pretty high level company, but I didn't know them at the time, so I agreed.
Art would flummox me with lefty twist serves, and consistent low dippers. George had few weapons, but could slice wide to my weak backhand pretty consistently. Art was 55, George a bit younger, and I, right now, can run circles around them, hit 25 mph faster serves with good placement, cover more than twice the court, and get to twice or 3 times as many balls. I cannot run now!
John basically could not move at all, so after 3 months playing with them, it was always me and John vs Art and George, always, to even out the sets.
You say, of course .... NO WAY, just a lie and a tall tale. How can that be, LeeD has played tennis for only 2 full year's then.
Consider this. LeeD played 3 year's of football for his high school in the fall, and 3 year's of basketball for the school in the spring. I graduated at 16 year's of age, at 5.6" and 117 lbs. That's one year of JV football, and 2 year's of varsity football for a school with 3,300 students and 700 in my class alone. In 11th grade, I started both ways in the AAA Championship game for Abraham Lincoln High in San Francisco.
There is no way, me at 68 years of age, and what I consider "can't run at all", would I ever lose to a real 3.5 level player.
My normal singles opponent's range in age from 15 thru 52. The younger two opponent's are No.s ONE, and 3 for their high school in tennis.
I am low 4.0, but can play dead even with them any day of the week.