Kyle Busch, Brad Keselowski trade insults on Twitter

Kyle Busch and Brad Keselowski, who have had many on-track skirmishes in recent years, mixed it up on Twitter Friday ahead of Sunday's Monster Energy NASCAR Cup playoff opener at Chicagoland Speedway.

After Toyotas swept the top four spots in the opening practice session, Keselowski, Ford's top driver in the point standings, tweeted, "Haven't seen NASCAR let a manufacturer get this far ahead since the 70s."

Busch's four-letter response: "STFU."

Not to be outdone, Keselowski fired back: "It's 2017. When you're about to lose an argument you call people names rather than face facts."

The two drivers later elaborated on their brief but nasty social media feud in interviews before qualifying Friday, with Keselowski telling NBCSN "it is still pretty obvious" Busch and other Toyota drivers have a technological advantage.

"You can BS through it any way you want, but it’s there and we know we’re going to have to out-execute ’em and we need a little bit of luck, because at this point in time, their cars have way more speed," Keselowski said (via NASCAR.com).

Busch countered by saying when Keselowski has had a faster car than him in the past, he and his team just worked harder to find speed.

“It takes a whole lot of hard work and dedication through a lot of great people, and I feel like right now all he’s doing is slapping his people across the face," Busch said.