ST. PETERSBURG — Helio Castroneves will be leading the pack one more time in Sunday's Grand Prix of St. Petersburg.Then the three-time winner on St. Petersburg's streets will have to pull off the track before the green flag falls. That's because this year Castroneves is the pace car driver.Being the grand marshal for the IndyCar season opener is a new role for Castroneves, the popular series veteran who is driving full-time for Roger Penske's Acura sports car operation this season."I'm still not sure what a grand marshal does," Castroneves said Thursday with a laugh.After 20 years in either CART or IndyCar, Castroneves is only driving in one IndyCar race in 2018, the Indianapolis 500, for Penske. In May, the Brazilian will try to become the fourth driver to win Indy four times."I never had the time to lay down and say, 'Holy moly, I'm not going to be driving an IndyCar anymore,' " Castroneves said. "Because I'm doing something really cool, racing sports cars, and it's still racing for Team Penske. … So the transition has been fairly easy. If you come back to me after the first practice I'm probably going to say, 'Sorry, man, but this sucks.' If that happens, it is what it is. But right now I'm very happy to see everyone."Castroneves will go down as a legend — three Indy 500 wins and 30 total career victories ensure that for anyone — but he leaves his full-time IndyCar career behind without a championship. He was second in points four times and finished in the top five 13 times."Why I didn't win? Destiny didn't want to make it," he said. "It wasn't because of lack of effort. I did everything I could; I feel that it wasn't meant to be."RELATED: Dancers, ninja warriors, bachelors … and IndyCar driversSeries deal extendedThe race's title sponsor and tire supplier, Firestone, announced a two-year sponsorship and race extension. Future race dates are March 8-10, 2019, and March 13-15, 2020. This weekend, Firestone and the series are in the final year of a three-year agreement.This is the 14th IndyCar race in St. Petersburg (15th including the one-off Champ Car edition in 2003) and the downtown streets are the setting for the series opener for the eighth consecutive year."The Firestone Grand Prix of St. Petersburg is a marquee event," said Lisa Boggs, director of motorsports for Bridgestone, which owns Firestone. "Street courses are very difficult to do. But when you've got the unwavering support of the city — the fans, the mayor, the city council, the folks at all the local businesses — that is probably Step 1. … And the folks at (race promoter) Green Savoree in leading this effort just do an amazing job."RELATED: Grand Prix of St. Petersburg schedule of events, ticketsNo longer the new kid in townDefending IndyCar champion Josef Newgarden set quite a standard for himself in 2017, winning the title in his first year driving for Penske.That championship also helped Newgarden, 27, shake the feeling of being the new kid at Team Penske after he spent his first five seasons with smaller teams."I felt awkward walking into the team," Newgarden said. "I went to the team shop in the offseason and there were over 400 employees. So it felt odd to be there. I was like, 'I don't belong.' Every time I would walk into the building I (thought) I hope security doesn't throw me out. So having a year under your belt makes a world of difference."