What happened: Haas sidelined Esteban Ocon for the remainder of the Mexico City Grand Prix. Reserve driver Ryo Hirakawa steps into the car starting with Free Practice 3 on Saturday. The FIA approved the formal driver change ahead of the session at Autodromo Hermanos Rodriguez.

Why it matters: The sudden switch hands Hirakawa his Formula 1 race weekend debut under abrupt circumstances. The move forces Haas to navigate qualifying and Sunday's grand prix with an untested driver lineup.

What to watch: Hirakawa takes part in Saturday's final practice session before heading directly into qualifying.