One year ago this week, Brian Vickers paced around his Southern California hotel room until he accepted the realization that his racing career was about to be interrupted by yet another blood clot scare.

He returned to Fontana on Friday with a good seat in a fast car and plenty of optimism about his racing future, which seemed fairly bleak only a year ago.

"I've never been the kind of guy to give up, and by no means was I giving up then, but I certainly didn't think I'd be sitting here (now)," Vickers said before NASCAR Sprint Cup Series practice.

"I wasn't sure what the future held," he added. "Because I was aware of the signs and symptoms, I did catch my blood clot early, and I didn't feel at all that my life was in danger. But I wasn't so sure about my racing career."

Vickers will drive Tony Stewart's No. 14 Chevrolet on Auto Club Speedway's weathered asphalt Sunday in his third start of the season. He is sharing the seat with Ty Dillon while Stewart's injured back heals from an offseason dirt buggy crash.

But even a part-time job with Stewart-Haas Racing is a joy for a veteran driver who ran only two races last year before getting sidelined by his third serious bout with blood clots.

Vickers missed the rest of his final season under contract with Michael Waltrip Racing. After NASCAR medically cleared him to return, he landed a job as Stewart's co-replacement.

"As much as I want to race this car as long as I can, because it's a great team and a great car and a great opportunity, I really want to see Tony back in it, because I've been in his shoes," Vickers said. "I know exactly what it's like. It's his last season. He deserves to be in this car as much as he can be, so I'm honored to race it as long as I need to and as long as I can, but I'm happy to turn the keys back over as soon as he's ready."

Vickers has endured repeated blood clot struggles and two heart surgeries in the last six years, but he returned to racing each time.

He missed races in 2010, 2013 and 2015 due to blood clots and the resulting blood-thinning medication, which would make it difficult to stop his bleeding in a serious wreck. Vickers had surgery in 2010 to fix a hole in his heart and another procedure in 2014 after his body began to reject the patch.

"It's been a challenging five, six years for me," Vickers said. "But in a weird way, I'm very thankful for those experiences. I've grown a lot as a person, and a lot of good things have come from it."

Indeed, Vickers' health condition boosted his mainstream celebrity since he appears alongside golfer Arnold Palmer, Miami Heat big man Chris Bosh and comedian Kevin Nealon in a series of advertisements for a blood-thinning medication.

"My story really resonates with a lot of people because I'm an athlete, and I'm young," Vickers said. "It's proof that this can happen to anyone."

After finishing 26th at Daytona and 36th at Las Vegas this year, Fontana could be a good place for Vickers to break out. He has run this race only twice in the previous five years, but he recorded two top-eight finishes in those starts.

Vickers is scheduled to drive for SHR again in two weeks at Martinsville, but his long-term future is still unclear, with Stewart working hard to return.

Although he has unexpectedly enjoyed the occasional weekend breaks created by the lack of a full-time job, Vickers is exploring possibilities for future challenges. He raced in the 24 Hours of Le Mans in 2012 while he lacked a NASCAR seat, and he has been mentioned as a candidate to run the Indianapolis 500.

"I am open to racing everything that has a seat, four wheels and a steering wheel," Vickers said. "I would absolutely go back to the 24 Hours of Le Mans. I would absolutely go back to the BC Series. I've had the opportunity to drive a lot of different cars in different series, and they're all amazing. I'd love to be back in a sports car again, or anything else that comes along."