NASCAR star Brad Keselowski has said he thinks he made Greg Biffle proud on Sunday at Darlington.

Biffle, who tragically passed away with his family in a plane crash late last year, was honored on the side of all three of RFK Racing's cars last Sunday, with the font of the drivers' numbers all changed to match Biffle's iconic 16.

The 19-time Cup Series race winner drove almost his whole Cup Series career for the team now known as RFK, in its previous iterations as Roush Racing and Roush Fenway Racing, before the Keselowski was added.

However, it wasn't his gutsy drive to second place on Sunday that Keselowski thought would put a smile on Biffle's face if he were there to see it. Instead, it was picking up an iconic 'Darlington stripe' down the right-hand side of his car.

NASCAR TODAY: Denny Hamlin issues retirement update and Kyle Busch talks Cup Series future

Keselowski: I think that would make Greg proud

Interviewed on pit road after the race, Keselowski said: "We didn’t have the best car today. Not compared to Tyler. Tyler drove a hell of a race, and he’s driving a rocket, and he’s making it count right now.

"I think we got the most out of the day we were getting to get, honest, but we scored a lot of stage points, second place, first place loser, but that’s okay. We’re doing the things we need to do and making the most of the days we have.

"It’s really cool to have the great group of cars running up front. I put a nice right-sided stripe on the car. I think that would make Greg proud. If you know Greg, you’ll understand that one. A good day for Solomon Plumbing Ford Mustang."

The result was the 42-year-old's best since badly breaking his leg in an off-season ski trip accident, coincidentally on the same day as Biffle's tragic passing.

He shared on social media at the time: "I broke my leg and was going into surgery when the tragic plane accident happened to Greg and his family. Not really sure the words to say so I’ll share a story:

"I called Greg a few years ago telling him my friend really needed a fun trip after losing a family member, could we all go ride his UTV’s together to show my friend a good time? Without missing a beat he made all the plans & we had a great sand dunes trip, my friend was all smiles. This trip means so much more now… this is my favorite Greg story, Will miss you and your family. #GodSpeed"

NASCAR STANDINGS: Tyler Reddick takes huge lead as multiple NASCAR champions demoted after Darlington