Jeff Gluck

USA TODAY Sports

Dale Earnhardt Jr., who has been out of his race car since July with a concussion, will miss the remainder of the NASCAR season, Hendrick Motorsports announced Friday morning.

Earnhardt has already missed six races and will now skip the remaining 12 events as he recovers. Jeff Gordon and Alex Bowman, who have both substituted for Earnhardt in the No. 88 car during his absence, will continue to split the schedule.

Gordon is set to drive the car this weekend at Darlington Raceway.

Earnhardt, who will be 42 on Oct. 10, has a history of concussions, the latest of which has caused him to have vision problems and balance issues.

“I wish I could return to the No. 88 team this season,” Earnhardt said in a statement. “To say I’m disappointed doesn’t begin to describe how I feel, but I know this is the right thing for my long-term health and career. I’m 100% focused on my recovery, and I will continue to follow everything the doctors tell me. They’re seeing good progress in my test results, and I’m feeling that progress physically. I plan to be healthy and ready to compete at Daytona in February. I’m working toward that.

“The support from both inside and outside the race team has been overwhelming. Everyone has been so encouraging and positive, from my teammates and sponsors to my family, friends and fans. It’s motivating and humbling at the same time.”

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Team owner Rick Hendrick said the organization wants Earnhardt to return, but "we want it to be for the long haul."

“I know how hard Dale has worked and how frustrating this is for him,” Hendrick said.

Gordon will drive in four more races: Darlington, Richmond International Raceway next week, Dover International Speedway on Oct. 2 and at Martinsville Speedway on Oct. 30, the site of his last win.

“Jeff and Alex will give us a great opportunity over the rest of the season," Hendrick said. "Jeff is one of the best of all time and knows our system. He brings things to the table that no one else can. Alex is a young driver with a lot of talent, and he will give us a fresh perspective. We know they’re not only capable of running up front and giving us a chance to win, but they’ll help us get better.”

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Earnhardt's most recent race was July 9 at Kentucky Speedway, where he had an uneventful 13th-place finish.

But the next week, Earnhardt was declared out for the race at New Hampshire Motor Speedway — a stunning development, since he had not crashed recently.

It turned out an accident in the June 12 race at Michigan International Speedway may have caused a concussion with delayed symptoms. Earnhardt initially thought it was a sinus infection, but after consulting with doctors and considering his history of concussions, it was determined his issues were actually a head injury.

In the time since, Earnhardt has been very open about his symptoms. Using his weekly podcast and social media, Earnhardt has described how he has trouble focusing on an object. The vision issues have also caused difficultly with his balance, and the two together mean he cannot get in a race car.

The driver, voted NASCAR's most popular for 13 straight years, has shown fans some of his rehabilitation exercises through Instagram videos. The rehab and recovery is being headed by Micky Collins at the University of Pittsburgh Medical Center's Sports Medicine Concussion Program. He also is being seen by Jerry Petty, a neurosurgeon in Charlotte.

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Earnhardt suffered at least three concussions in his career before this one. In 2002, he suffered a concussion at a race in California that he hid for weeks. In 2012, he had two concussions six weeks apart that forced him to miss two races.

Some of NASCAR's concussion protocols have been driven in part by Earnhardt, who earlier this year pledged to donate his brain for research. Shortly after Earnhardt's 2002 concussion, the sport said doctors at every track's infield care center could mandate that drivers have CT scans or MRIs if there was the possibility of a concussion. And drivers must get a medical release before returning to the car if they are diagnosed.

In preseason 2014, NASCAR mandated all drivers must undergo baseline testing.

Earnhardt is engaged to Amy Reimann and has said he plans to get married in the offseason.

Earnhardt is the son of seven-time NASCAR champion Dale Earnhardt, who was part of the NASCAR Hall of Fame's inaugural class. But while Earnhardt Jr. has never won a Cup championship, he's made a racing legacy of his own.

In addition to two Xfinity Series championships, Earnhardt has won 26 Cup races — including two Daytona 500s. His resume includes six victories at Talladega Superspeedway, tied for the second-most all-time behind his father's 10.

Earnhardt also co-owns the JR Motorsports team, which races in the Xfinity Series, and is a successful businessman.

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