Michael Waltrip Racing's Brian Vickers has revealed that the latest recurrence of blood clotting issues will sideline him from the NASCAR Sprint Cup Series for at least three months - and potentially permanently.

"Unfortunately, now I am back on blood thinners for at least three months and through those three months I'll try to figure out what makes sense with my doctors if I can come back off of them to go racing," said Vickers in a press conference in California on Sunday.

"If there's some kind of plan that works and if not, then that's that."

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NASCAR won't allow anyone to race while on medication for blood clotting, as it can contribute to uncontrolled bleeding if a driver is involved in a serious racing accident. As long as Vickers is on the medication, he won't be allowed back behind the wheel of a race car.

The concern is that if the recurring problems with clotting that Vickers has experienced since 2010 require him to be on the medication long term, then this could spell the end of his racing career entirely.

"Am I worried? Of course," Vickers said. "Have I given up hope? No.

"I don't know what's next," the 31-year-old admitted. "I know I will be on blood thinners for the next three months and then after that I'm going to do whatever I can to get back in a race car, but what's next is next and we'll cross that bridge when we get there.

"No matter what, I appreciate the support [that I've received]," he added. "The support in the NASCAR community has been amazing every time and every step of the way as I expected it to be from the fans to the media to the people in the garage. Thank you for all of that."

Vickers missed most of the 2010 season with blood clotting issues that also resulted in surgery for a hole in the heart. He returned to competition in 2011, but had a recurrence of the clotting problems at the end of the 2013 season. Last December, he also underwent a further heart procedure to replace a patch used in the original surgery four years previously, which meant that he missed the first two races of this year's NASCAR Sprint Cup Series.

Despite making a full recovery in time to return to duty at Las Vegas, Vickers told reporters that he started to experience new symptoms of chest pain on Thursday while on a flight from New Orleans to Las Angeles.

"I went to the hotel to check-in because I was still trying to convince myself it was something else," Vickers said. "I sit there for a few minutes and kind of paced the room with [my wife] Sarah and was trying to figure out if I could turn my chest pain into something that it wasn't.

"I told her that if I go to the hospital, I'm not racing this weekend," he continued. "She was very sweet and encouraging. She was like, 'You don't know that yet. Let's just go get it checked out.' I was like, 'Yeah. I know.'"

Sure enough, the doctors at the UCLA Hospital in Santa Monica confirmed what he had feared. "I had small blood clots in both lungs," Vickers said. "And that's that."

Vickers said that the pain - which he put at a five initially - has considerably subsided now that he is back on medication. Vickers' Sprint Cup car had been due to be sponsored at Fontana by Janssen Pharmaceuticals who make an anticoagulant medication called Xarelto; the driver confirmed that he had not been taking that since 2013 or had been on any other blood thinning medication in recent weeks leading up to the recurrence of the clotting problem, because of his return to racing.

Brett Moffitt - who previously deputised for Vickers in February when Vickers was still recovering from surgery - was once again tapped to fill in for him in the #55 entry in Sunday's Auto Club 400. MWR is yet to decide what will happen with the car in the longer term.

"Absolutely zero has been decided moving forward at this point because it has all been focused on doing the right thing this weekend and understanding a little bit more about what Brian's situation is," said MWR executive vice president Ty Norris earlier in the day.

"In the last 48 hours, there have been a million thoughts that have crossed everyone's minds," Norris told ESPN.com. "When we gather all the facts, we'll sit down as businessmen and decide what we're going to do."

Vickers' contract with MWR expires at the end of the current season, and if the team opts not to extend it then the driver could find if difficult to find a new seat elsewhere given his recent health history.

"They have a team to run, and I'm probably starting to wear out their patience," Vickers conceded. "But I know that if at all possible, they're going to stick behind me and they've proven that."

If his racing career does end up being put on a longer indefinite hold as a result of the latest health setback, then Vickers insists it won't be the end of the world for him.

"I love racing more than any other activity," he admitted. "But I don't love it more than my wife, who takes good care of me, or my family or my friends. It's not who I am, it's something that I do, something that I love doing.

"There's more to life than just this," he insisted. "I think keeping that perspective is important, but it's also my favourite thing to do in the world. I want to try to come back.

"It's pretty frustrating, but hey, I've been here before," he added. "I've been told now three times that I'll never race again, and I've raced the last two weeks.

"That's life. You've got to keep fighting. You can't give up. You never know what tomorrow holds."