The current IndyCar grid consists of drivers from all motorsport disciplines, like former F1 driver Marcus Ericsson, former V8 Supercars driver Scott McLaughlin, F2 driver Marcus Armstrong, and more. Unlike the European open-wheel racing scene, where drivers progress up the Formula ladder, drivers from all around the world and of various age groups make their debut in IndyCar.
As a result, some experienced motorsport drivers, including the likes of F1 World champions, have entered the IndyCar championship as rookies and even won the championship. Let's have a look at the Top 5 drivers who impressed in their rookie season in the American open-wheel racing series.
#5 Alex Zanardi
Alex Zanardi arguably had one of the greatest rookie seasons in IndyCar during the 90s. The Italian raced in F1 for four seasons before making a switch to IndyCar in 1996. Zanardi finished his rookie season third in the championship with 132 points and three wins to his name.
The Italian driver won consecutive IndyCar championships in the next two years with Chip Ganassi Racing before returning to F1 for the 1999 season.
#4 Bobby Rahal
Bobby Rahal raced in the F1 championship in the late '70s as a part-timer before making his IndyCar debut in 1982. Rahal signed with Truesports. Co for the 1982 season and finished as the runner-up behind the champion Rick Mears. Rahal won two races in the 11-race calendar and finished on the podium six times.

The rookie season laid a concrete foundation for Rahal to solidify his position within the team, as he went on to win three IndyCar championships.
#3 Teo Fabi
Teo Fabi was the next big phenomenon in IndyCar after Bobby Rahal. The Italian made his debut the very next year after Rahal’s debut, i.e., in 1983, and like Bobby, finished runner-up in the championship. However, the Italian had four wins to his name. He notably took the pole position for the 1983 Indy 500 but retired from the race.
Fabi simultaneously raced in F1 and IndyCar for the next few seasons but didn't win any championships in either of the open-wheel racing series.
#2 Nigel Mansell
Nigel Mansell decided to take on the IndyCar challenge after winning the F1 championship in 1992. Mansell joined the Newman/Haas Racing team for his rookie season and was partnered alongside F1 and Indycar champion Mario Andretti.

Nonetheless, it was Mansell who came out on top in his rookie season as he won the championship with five wins to his name. He raced in IndyCar for another year after winning the championship before moving away from the sport.
#1 Juan Pablo Montoya
Juan Pablo Montoya started his career in the junior Formula categories before moving up the ladder and becoming a test/reserve driver. However, the Columbian didn't get his big break in F1 for a couple of years and decided to move to the US to race in the IndyCar championship.
Montoya signed with Chip Ganassi Racing for the 1999 season and won the championship. The Columbian finished the season tied on points with Dario Franchitti, but had seven wins to his name compared to Feanchitti’s three, and hence was declared the champion, and the rookie of the year.