Australia's defending champion Will Power has crashed out during the opening lap at the IndyCar race at Exhibition Place in Toronto, won by Josef Newgarden.
Power, starting in fourth, hit New Zealander Scott Dixon's rear at the third corner of Sunday's race, causing him to bounce into the wall.
He limped through the remainder of the lap before calling an end to his day and claiming last place.
"I went down the outside of Scott and I don't know if someone was on the inside of him (but) he moved out pretty quickly," said Power, who claimed his third of four wins for 2016 in Toronto.
"Unfortunately, we ended up in the wall.
"I should know better than to ever take any sort of risk when it's the first lap, it's just not worth it."
Meanwhile, Newgarden, ranked one ahead of Power in championship standings in fourth, raced to his second Toronto title in three years.
The American came out in front on lap 25 after a crash by Tony Kanaan caused a caution, maintaining an advantage of more than two seconds for the majority of the rest of the race.
Kanaan had his brakes lock up while leaving the pits and connected with the protective tyres on turn one.
The caution caused the top-three cars of Helio Castroneves, Simon Pagenaud and Graham Rahal to fall back.
Newgarden claimed his fifth career victory, also winning in Alabama in April.
"I think that is twice I have had good calls and got into the pits at the right time," Newgarden said.
"I thought we had a very fast car, we got a pretty good start, and stayed out of the mayhem. Very, very happy for all of Team Penske."
Alexander Rossi was second for his first podium finish of the year and best since winning the 2016 Indianapolis 500.
James Hinchcliffe finished third in his hometown race for the second straight year.
Marco Andretti was fourth, followed by pole-sitter Pagenaud, Ryan Hunter-Reay, Max Chilton, Castroneves, Rahal and series leader Dixon.
Dixon has a three-point lead over Castroneves with five races left.