Stewart underwent his third operation on Oct. 7, and said during a video chat Tuesday night on NASCAR.com that the risk of infection was something doctors had warned him about after his injury in an August sprint car crash.
"I was more worried about bones healing and skin healing," he said. "The doctor was more worried about infection and really said the first two months were kind of the critical time. We were at the end of that two months for the most part and, all of a sudden, a spot popped up that was infected and that caused the surgery last week. I went from starting to walk again, not great, not just walking around the house like normal, but I could take eight or 10 steps at a time, to having to spend the majority of the day again laying down."
Stewart is still on track to be back in the car for the season-opening Daytona 500.
During the chat, Stewart fielded questions from fans who submitted them through social media. He was asked what his biggest concern was before NASCAR's inaugural Truck Series race this year at the Stewart-owned Eldora Speedway dirt track.
"Weather. That was the one thing we couldn't control was the weather," Stewart said. "It's not like a pavement track where you can bring a jet dryer out and two hours later have the track back in shape.
Asked if NASCAR would ever race Nationwide or the Sprint Cup Series on dirt, or at Eldora, Stewart said he didn't know.
"I never thought I would see the Truck Series there, the Truck Series proves that anything can happen," he said.
Stewart also said participation in the Coca-Cola's promotional Racing Family has helped mend relationships between drivers. He feuded with Joey Logano earlier this year, and Logano and Denny Hamlin are still not on speaking terms following a series of early-season incidents that culminated in a last-lap accident between the two at California in which Hamlin suffered a fractured vertebra.
All three drivers are in the Coca-Cola family, which requires several appearances together and commercial shoots.
"The outtakes are almost better than the commercials," Stewart said. "When you hear everybody talk about the Coca-Cola Racing Family, it really is a family. It's a family atmosphere. Even the dysfunctional family that we are with Denny and Joey and myself now, we are the three brothers that disagree sometimes. But still when we do this stuff, we still get along with each other, we still have fun, and we all forget about the stuff that happens on the race track.
"It's one of the few opportunities where we get to be around each other and not worry about racing."
BIG GOAL: Roger Penske isn't mincing words when it comes to the task at hand for Helio Castroneves in Saturday night's season finale at Auto Club Speedway in Fontana, Calif.
"Well, Helio's got to win the race, and it's a longshot," Penske said.
Castroneves trails IndyCar Series points leader Scott Dixon by 25 points going into the final race. The Brazilian had led the standings for 12 consecutive races before losing the lead to Dixon two weeks ago when his gearbox broke 10 laps into the second race at Houston.
In all, Castroneves led the points 14 of 18 races this season.
But he had a terrible weekend in Houston, where Castroneves had taken a 49-point lead over Dixon into the doubleheader. Then Dixon won the first race and Castroneves had a gearbox issue, and Dixon finished second in the second race when Castroneves had a catastrophic failure.
"We shot ourselves in the foot in Houston with the problem with the gearbox," Penske said. "He got a little wide with the 10th lap and the bottom broke the gearbox. To me, its reliability and that's one of the ways you win championships. We were good right up until the last weekend, and then we fell on our face."
If Castroneves doesn't rally, it will be the sixth time Penske has come up short since Sam Hornish Jr.'s 2006 title.
Penske said he won't hold it against Castroneves, who also came up short to Dixon in 2008 when Dixon beat him by 18 points even though Castroneves won the season finale.
"Helio's done a great job all year and he can hold his head up high and he's going to drive for us next year, we've got to move on," Penske said.
GIBBS RECALLS TAYLOR: Jury selection began this week in Florida in the first-degree murder trial of the man accused of killing former Washington Redskins player Sean Taylor. Former Washington coach Joe Gibbs talked about the All-Pro safety over the weekend at Charlotte Motor Speedway.
"I really think that had he not had such an awful thing happen to him, he would have wound up having been one of the greatest players ever to play in the NFL," Gibbs told The Associated Press. "He was an unbelievable athlete, plus his competitive spirit. Plus he was physical, boy, was he physical."
Taylor was at his Miami-area home nursing an injury late in the 2007 season when a group of young men attempted to burglarize his home. Taylor confronted them with a machete, was shot once in the upper leg, causing massive blood loss that led to his death a day later at age 24.
Gibbs said he'd never been through anything like Taylor's death in his coaching career, and the toll it took on his team was enormous. He praised Redskins owner Daniel Snyder for flying the entire team to Florida to a ceremony honoring Taylor, and Gibbs said the players responded "the next four games were the best games I've ever had a team play for me.
"I think that was part of trying to make a statement. We put ourselves in the playoffs with that and I think that was kind of testimony to Sean," Gibbs said.
Gibbs retired for good at the end of the season and returned to NASCAR, where the next season saw Joe Gibbs Racing move to Toyota and the eventual departure of team leader Tony Stewart. It's been eight years since Stewart won JGR its last Sprint Cup title, but Matt Kenseth currently has JGR out front with a four-point lead in the standings at the halfway point of the Chase for the Sprint Cup championship.
WILSON RISING: With a pair of strong finishes in Houston, Justin Wilson made this one of the best IndyCar seasons of his career.
Wilson goes into the season finale race at Fontana ranked fourth in the standings, and although he's still searching for a win this year, his four podiums this season are the most since he had five in Champ Car in 2007.
Wilson has one more shot at picking up a win this year, Saturday night at Auto Club Speedway, where he'll be making the second start of his career. He ran just 80 laps in last year's race before a gearbox issue led to an early exit and a 23rd-place finish.
After a successful test at the track last month with his Dale Coyne Racing team, Wilson is confident for a strong finish to the season.
"We had a good test at Fontana," said Wilson. "We started out pretty steady and found some grip and improved the balance. We were within tuning range for the race so I'm hopeful for another positive result for us out in California this weekend."