Penske's Josef Newgarden has hit out at IndyCar rookie Santino Ferrucci for causing the championship contender to spin at the last corner of the Gateway race.
Dale Coyne Racing's Ferrucci had led 97 laps of the total 248 laps before he dropped to sixth due to an untimely caution but recovered to fourth at the flag.
He cleared Newgarden's title rival Alexander Rossi for fifth before passing Newgarden late on but had to cede the position when an attempted outside pass on Ed Carpenter caused him to lose momentum.
Ferrucci then hit back at Newgarden but suffered a wild moment up off-line at Turns 3 and 4 on the final lap and he returned to the racing line just as Newgarden arrived, forcing the Penske driver onto the grass and into a spin that cost him two places.
Newgarden told NBC Sports Network: "Look, it's important to know he's a rookie. What he did, in my opinion, is dangerous.
"He came over to talk to me afterwards and said he was loose, that's why he was down there, but I've been in the same position tonight, I know what it's like to get up in the marbles. He got up there a couple of times.
"He came directly back down on the racing line to try and block at the end, and there was no reason to.
"I gave him the [fourth] position twice because I was suffering [tyre] vibrations all night and my car was getting quite difficult to drive at the end of that stint. So I let him go two times during the night.
"But he's got to learn that this is big-time auto-racing; if you do a move like that on an oval, particularly a high-speed oval, you will cause a very serious wreck.
"And he's just gotta know that. I really drilled into him that you cannot come directly to the racing line. That was his instinct - to come right back to the racing line.
"You know, he's a racer, you're gonna have instincts like that, but you cannot do that in oval racing. It's absolutely not OK.
"It's a lesson. I hope he learns that and he gets that in his head."
IndyCar tweeted the interview earlier today, and Ferrucci responded.
Ok 2 things. First, I told him I was sorry and I was getting out of the marbles so I didn't hit the wall myself. Second, Last lap last corner! I'm not PULLING OVER to let Josef by! I'm a damn racer, I have a championship I'm competing for too. https://t.co/pp0xA3Ggka— Santino Ferrucci (@SantinoFerrucci) August 26, 2019
Ferrucci is referring to the rookie of the year standings in which his second consecutive fourth-place finish has earned him a narrow lead over Chip Ganassi Racing's Felix Rosenqvist, as well as ninth overall on the points table.