You save a little bit more the body.
At the start of this week in Shanghai, Del Potro was placed 25th in the race to London despite reaching the US Open semi-finals, knocking out Roger Federer at the quarter-final stage.
Sixth-seeded Grigor Dimitrov also advanced, but had to save three match points before beating Ryan Harrison 3-6, 6-3, 7-6 (6).
Del Potro required four match points - two on Zverev's serve in the ninth game, two on his own serve in the 10th game - to win this first encounter against the German.
The victor of that match may well meet Roger Federer in the semi-finals - a man whom Del Potro downed at the US Open.
"I played a very good match, I don't know how many mistakes I made, but very few", said the 16-time Grand Slam victor and top seed in Shanghai.
The talented 20-year-old Zverev was going after his sixth title of a breakthrough season and was comfortable in the first set against Argentine Del Potro, the 2009 US Open champion and 16th seed. "I just had to find my way through the whole match".
"I saw his frustration, for sure".
With his concentration clearly shot there was nothing the youngster could do to turn his fortunes around, and Del Potro went on to take the decider 6-4. "But I think he's still very young and he needs to keep learning, as he's doing now", said the Argentine, 23 in the world.
In other third-round action, Spain's Albert Ramos Vinolas stopped German Jan-Lennard Struff 7-6 (7-4) 6-4.