Kevin Harvick and Jimmie Johnson may be close friends, but that did not stop the defending Sprint Cup Series champion from giving the Hendrick Motorsports driver a jab in the chest after Sunday's race at Chicagoland Speedway.

The incident, which occurred in the driver motor home lot after the race, stemmed from a restart in which Johnson made contact with the right side of Harvick's car, cutting his right rear tire. The tire eventually went down, sending Harvick's No. 4 Chevrolet into the outside wall and resulting in a 42nd-place finish.

Johnson refused to take blame for the contact and attempted to discuss the incident with Harvick after the race in the motor home lot, but Harvick was having none of it. Immediately after walking out of the motor home, Harvick gave Johnson a jab in the chest and had to be restrained by business manager Josh Jones. As Harvick jawed away at the six-time champion, Johnson walked away shaking his head.

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Despite the physical confrontation after the race, NASCAR officials confirmed to FOXSports.com that neither driver would be penalized for the incident.

NASCAR executive vice president and chief racing development officer Steve O'Donnell joined SiriusXM NASCAR radio's "The Morning Drive" to discuss the post-race confrontation, saying, "There won't be any penalties."

"We look at that ... as emotion coming out when the stakes are really high in the Chase," O'Donnell told SiriusXM NASCAR raido. "That's a reigning champion who finds himself in a tough spot with two races and really needing a win, so you understand the frustration there. Obviously, you don't like to see what happened, but from our standpoint that's just pure emotion coming out when the stakes are high and knowing how important it is to go out and win a championship."

With the format moving to an elimination playoff system last year, intensity on and off the track ramped up during last year's Chase for the Sprint Cup. After an on-track incident during the Charlotte Motor Speedway Chase race, Denny Hamlin attempted to go after rival Brad Keselowski in the garage, but was restrained.

Hamlin's Joe Gibbs Racing teammate Matt Kenseth had better luck, trying to tackle Keselowski between the haulers. The two crews then got into a shoving match as they tried to separate the drivers.

Three weeks later, Keselowski found himself in another scuffle, as Jeff Gordon confronted him after on-track contact cut Gordon's tire and hurt his chances to advance to the Championship 4. After a well-time shove by Harvick to Keselowski, a brawl erupted on pit road with both drivers and crew members walking away bloody.

The footage has become a staple for promoting the intensity of the Chase. Neither driver was penalized, but both crew chiefs were fined and four crew members were suspended.

While none of the Chase drivers were fined for their post-race antics, NASCAR did issue fines to Casey Mears and Marcos Ambrose after a confrontation in the garage after the April 2014 Sprint Cup race at Richmond International Raceway. Unlike the Johnson-Harvick incident, Ambrose landed a punch on Mears' face.

Fights and confrontations have long been a part of NASCAR history, and the Johnson-Harvick incident is just the latest in the string of post-race excitement.