Earnhardt, who has concussion-type symptoms, will sit out Sunday's race at Indianapolis Motor Speedway and the following race at Pocono on July 31.
Gordon's return isn't just a four-time champion coming out of retirement to race. Gordon, who never ruled out an occasional return when he stepped out of the Hendrick Motorsports No. 24 car at the end of the 2015 season, returns this weekend to the track in Indianapolis where he has won five times, including the inaugural Brickyard 400 in 1994.
Gordon, 44, competed in 797 consecutive races from the season finale in 1992 through the end of 2015. He won 93 races -- third on the all-time Sprint Cup list --- and championships in 1995, 1997, 1998 and 2001.
Gordon has attended all but a couple of races this year, having spent the first 16 points races of the 2016 season as part of the three-man booth for the Fox Sports telecasts of Sprint Cup practices, qualifying and races.
"I think Jeff will do well," team owner Rick Hendrick said Sunday when talking about the possibility of Gordon's return. "He's won that race a lot of times.
"He's been out of the car this year. I expect if he gets in the car, he might be a little bit rusty, but we've got a lot of practice time and I don't think it'll take Gordon long to get back in the groove."
Whether Gordon continues in the seat, if needed, has yet to be determined.
"Jeff's a team player," Hendrick said in a news release Wednesday. "I know he'll be ready, and I know Dale has incredible trust in him. It's going to be an emotional weekend [at Indianapolis] with Dale not being there and seeing Jeff back behind the wheel."
Gordon's wife, Ingrid Vandebosch, tweeted her support.
Earnhardt said, in a recording he made Sunday night for his weekly podcast released Monday, that he was battling balance and nausea. It is possible the concussion symptoms are the result of crashes June 12 at Michigan and July 2 at Daytona. His ImPACT test, a cognitive examination that among other things tests memory and reaction time, showed results equal to his most recent baseline test, Earnhardt said.
Earnhardt missed two races in 2012 because of two concussions over a six-week span. "[My doctors] can give me a lot of exercises that retrain my brain to handle what I need to handle -- it's just going to take a lot of patience," Earnhardt said. "I take my health and quality of life as a top priority. ... I am going to take this slow and strictly take the advice of my doctors."
Earnhardt underwent further evaluation Tuesday at the University of Pittsburgh Medical Center Sports Medicine Concussion Program. Hendrick Motorsports said he will not travel to Indianapolis or Pocono.
"Our focus is giving Dale all the time he needs to recover," Hendrick said in the Wednesday news release. "There's nothing we want more than to see him back in the race car, but we'll continue to listen to the doctors and follow their lead. What's best for Dale is what's best for Hendrick Motorsports and everyone involved with the team. We're all proud of him and looking forward to having him racing soon."
The return of Gordon, despite the circumstances, could give the Indianapolis race a boost. He moved to nearby Pittsboro at age 14 and is a favorite of the local fans.
"That's going to be really cool ... if we get to race Jeff one more time," three-time Cup champion Tony Stewart, who will retire from Cup racing after this season, said Sunday.
Gordon's return to racing could impact his NASCAR Hall of Fame induction date. The current eligibility requirements for a driver under 55 or a driver with less than 30 years of competing in NASCAR is two years of retirement before being nominated. His tentative date was nomination for selection in 2018 for the 2019 class.
A NASCAR spokesman said his eligibility status likely won't be reevaluated until it becomes clear how many races he will run in place of Earnhardt.
All of Gordon's previous starts have come in the No. 24 car, now driven by Chase Elliott. While Gordon will drive a No. 88 car at Indy, his longtime sponsor, Axalta, already was scheduled to be a sponsor of the Earnhardt car for Indianapolis. The company, formerly the DuPont paint division, has a long association with Gordon and already had agreed to sponsor four of the next five races for the No. 88 car.
By missing Indianapolis, Earnhardt most likely will fall from 16th in the Chase qualifying standings to outside the bubble to make the 16-driver Chase. He currently has a 14-point edge on Trevor Bayne for the final playoff spot.
There will be six regular-season races remaining after Indianapolis. If he returns during the regular-season portion of the schedule, Earnhardt would need a waiver from NASCAR (and it's expected he'd get one) to miss races and still be eligible for the Chase. The regular-season champion plus the next 15 drivers, based on wins with points as the tiebreaker, make the Chase as long as a driver who wins is in the top-30 in the point standings. Earnhardt is winless this year.