Ask Dale Earnhardt Jr. what he'd ideally like for his 40th birthday, and inevitably top of the list would surely be his very own NASCAR Sprint Cup Series championship, the title he's been chasing without success to date for over a decade.

This weekend, Earnhardt - the most popular driver and with the most famous name in US motorsports - is at Charlotte Motor Speedway to celebrate that landmark life event, but he does so in the knowledge that the very next day could determine whether or not his 2014 title hopes carry on into November.

Earnhardt is currently the 11th out of 12 drivers in the Chase championship play-offs - and next weekend will see the bottom four drivers cut from the field at the climax of the Contender Round. Earnhardt was one of a number of drivers to suffer a costly tyre failure last week at Kansas Speedway which put him into the wall and consequently on the ropes in terms of making it through to the third round of the play-offs.

"We obviously know what the situation is with the points and how important it is for us to come in here and win the race," said Earnhardt, determined to find the silver lining of the situation. "I have been winless at Charlotte in a points paying race since I started my career, so it's bound to happen sooner or later. I always win at the weirdest times in the oddest circumstances. So I feel like everything is lining up and feel real good about this weekend.

"We still feel like we have a shot, there is a chance," he insisted. "That is all you want to be able to go out there with a good attitude and try to make it happen. There are two races left, but I would like to make it happen this weekend because like I say I haven't won a points paying race here. That would be just amazing for us to go ahead and get that done with the circumstances that we've got."

The old Chase format was something of a mini-marathon that rewarded consistency, and Earnhardt said that in his view the new system of three 'sprint' rounds followed by a final winner-take-all race at Homestead-Miami Speedway was better for him, even in the current circumstances.

"Last year if we had hit the fence last year in one of those races you would pretty much of written yourself off at that point because you are competing against some guys that are so consistent," he said. "With this system we still feel like we are in it. Feel like if we believe in ourselves and believe in what we are doing we can go out there and get in the mix.

"I feel less pressure now I think than I did before the race at Kansas. Even if we had run in the top five last week I think today still under the circumstances now I still feel less pressure for some reason, it's weird.

"There are two kinds of approaches [to winning the Cup title] and they are both equally as nerve-racking. The one approach is to run well and hope that nothing bad happens, and the other approach is if something has happened you can really just kind of go for broke," he explained. "I just think that we have a shot and I feel good about it. I think our team is good. I think we are good enough. I think we should go out there and win. I believe we will."

In the meantime there's a birthday to celebrate, with Earnhardt insistent that he wasn't about to let last week's setback at Kansas get to him and spoil the occasion.

"I think that probably has a little bit to do with my disposition," he suggested. "I felt like as soon as what happened last week happened I think that I sort of had to switch into this mode and get ready for our opportunity here this weekend. I just was so happy with the way that car ran last week and how fast we were.

"I feel like we have a great opportunity this weekend. I think I would feel that way no matter what week it was, no matter whether I was having my birthday or not ... We will hopefully win the race and that will be the biggest [birthday] surprise."

Inevitably, turning 40 can't help but make Earnhardt think about getting older, what he's achieved to date and what he still wants to do before time runs out for his racing career, which as car as he's concerned remains a very long way down the road.

"I think that 40 to me means, 'Whoa, I've still got a lot of fun stuff I want to do, slow down!'" he said. "I'm like ageing in literal years faster than I am physically and mentally. I feel like I just have a lot of things that I've yet to accomplish, not only in racing, but in life in general, lot of fun that I'm not done having.

"I feel great. You kind of reflect a little bit and you think about how lucky everything has worked out and how fortunate," he added. "I mean I've had so much fun. Done a lot of great things and been a lot of crazy places and have had some fun times. Hopefully, the next ten [years] will be just as good and we will just keep going.

"Definitely being 40 has been an awesome time," he continued. "This week has been full of surprises and pleasant stuff happening left and right," including a surprise party on Monday and the presentation on Thursday of a US Legends Dirt Modified car from Charlotte Motor Speedway that is an exact replica of a car Earnhardt drove there as a teenager.

"That is exactly the way the car looked," Earnhardt told track president Marcus Smith and Speedway Motorsports executive Don Hawk. "That was my very first race ever right there ... What a nice looking little piece there. This track and you guys, especially you two, mean a lot to me, and continue to be great friends of mine, and I really appreciate that."

But birthday surprises aside, Saturday is the day that really matters. Although there will still be a Hail Mary chance for a race win next week at Talladega if things don't go to plan here, Earnhardt is all too aware that this weekend at Charlotte is his last chance to really take control of his own fate in the play-offs.

"You can't really go into Talladega with the same confidence because it's such a lottery there on how in the hell you are going to finish. I want to make it happen now. I feel like I've got a better chance today, this week than I do in Talladega even with the success we've had there.

"It's just who is going to show up Saturday night and win the race," he summarised. "We are back in a situation we have our backs against the wall, but we are in a situation where we can be aggressive again, as hard and crazy as we want to be on pit calls and fuel mileage and all those things.

"I'm not even counting points or worrying about scenarios and numbers and figures," he said. "I just have to go try to win this race."