Del Potro, of Argentina, lost to Novak Djokovic in straight sets in the US Open final.
Djokovic will play for Team Europe at the Laver Cup, which begins Friday at United Center. Each team has six players, including Roger Federer (Team Europe) and Kevin Anderson (Team World). The event features best-of-three-sets singles and doubles. The final is Sunday.
Tiafoe played for Team World at the inaugural Laver Cup in Prague last year. He lost to Croatia's Borna Coric in a deciding five-set match in the Davis Cup semifinals last weekend.