Jeff Gordon says he's ready to step in for Dale Earnhardt Jr. this weekend at Indianapolis Motor Speedway, and confident he can do a credible job as Earnhardt continues to recover from concussion-like symptoms.

Gordon, 44, also said he is well aware of the unique challenges he'll face while getting in a NASCAR Sprint Cup Series car in the heat of summer for the first time since last November's season finale at Homestead-Miami Speedway. Gordon retired as a full-time driver in the series at the end of last season.

"They know that I'm old and not in the kind of shape that I was. But of any track we could come to -- heat or no heat -- where I feel like I could come to and do a good job, it's right here at Indianapolis," Gordon said.

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Gordon will be making the 798th start of his career in NASCAR's top series. He ranks third all-time with 93 race victories, trailing only Hall of Famers Richard Petty and David Pearson.

But no one has won more times at Indianapolis Motor Speedway -- and that includes all forms of motorsports.

Gordon's five career wins at the 2.5-mile track are the most in NASCAR and tied with former Formula One driver Michael Schumacher for the most in all of auto racing.

Gordon said he woke up Friday morning pleased to see that Earnhardt had tweeted that he was finally beginning to feel better.

"I certainly woke up feeling good when I saw Dale Jr.'s tweet that he's seen progress," Gordon said. "I texted him right away, as soon as I saw that. So that's great news, a great way to start the day."

Gordon then recounted how Rick Hendrick, owner of Hendrick Motorsports and the only car owner he has ever driven for in NASCAR's top series, repeatedly texted and called him while he was in France on vacation with his wife, Ingrid, last week.

"I questioned Mr. H several times when he was asking me on the phone about this," Gordon said. "But that confidence they have in me, and then to go spend time with the team ... Dale's got a great team. I'm so impressed with (crew chief) Greg Ives and the 88 team."

Hendrick eventually talked Gordon into coming back, and has said that the four-time championship drive will be in the No. 88 for Earnhardt for at least this Sunday's race at Indy and next Sunday's Sprint Cup race at Pocono Raceway.

"I'm certainly a little overwhelmed with everything that's happened in the last week," Gordon said. "But most of all, I'm proud to be here and help his team out. This is Dale's team. What we want most of all is for him to be healthy for the long haul, and hopefully this is a good sign of things to come for him.

"For me, my goal is to come here and give the team the best effort that I can, and the get them the best result. Hopefully it's a good one."

Gordon added, again, that he understands the challenges he faces -- and that he hasn't had a whole lot of time to properly prepare for them.

"There certainly is a lot of preparation that goes into every race and every season, for the driver and the team," said Gordon, whose last win at Indy came in 2014. "All I can I can tell you is that I've done everything I could possibly do over the last three days to get ready for this race the best way that I can.

"We'll find out what kind of conditioning I'm in. There certainly will be challenges this weekend. ... But Rick and the whole team has given me a lot of confidence by choosing me and asking me to do this."