Talk about a smooth operation: Formula 1 star Carlos Sainz enjoyed a perfect day at the tennis on Wednesday at the Rolex Monte-Carlo Masters—which included a meeting with two of the biggest names in the draw. The Ferrari driver is a regular visitor to the ATP Masters 1000 tournament, which has become one of the Principality’s favorite events on its glittering social calendar frequented by celebrities, actors and, of course, Formula 1 drivers like Sainz. The Spaniard was one of several drivers...