Marcus Armstrong was on track for his first IndyCar win at the XPEL Grand Prix at Road America before a mechanical failure forced him to retire with just four laps remaining.
Armstrong had outlasted a chaotic 55-lap race, featuring five cautions, to take the lead. He was out front for 14 laps after starting third.
The New Zealander's loss is a significant blow, given his strong performance throughout the race. The incident will be a disappointment for Armstrong, who was poised to claim his first IndyCar victory.
