Tony Stewart has confirmed that the recent third operation he underwent at the start of the month had been unplanned and unexpected, and followed the discovery of an infection in his right leg that had previously sustained a broken tibia and fibula in a racing accident in August.

"They said after we got through with the second operation that the first two months was critical as far as the risk of infection," Stewart said in a video chat on on Tuesday evening from Charlotte, North Carolina. "I never dreamed I'd have to worry about it.

"I was more worried about bones healing and skin healing," he admitted. "[But] 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 ten steps at a time - to having to spend the majority of the day again laying down," he added, admitting for the first time that this latest procedure had been "a little bit of a setback" in his recovery.

"Hopefully only two or three weeks, but still a setback," he conceded. "We were virtually at the end of that cycle that they were worried about, time-frame wise, and then all of a sudden ... We thought we were out of the woods with the infection part really. It was in a section, the only spot that didn't heal."

Stewart insisted that the infection hadn't been the result of a lack of care or caution on anyone's part. "We did a pretty good job of keeping it clean, doing everything the first couple of weeks as far as staying off it the way we were told to give the skin time to heal," he said. "It literally just came down to one spot under the skin; something was going on down there that it didn't like, it showed up on the surface and then we realised we had a problem."

Stewart described the affected area as being "about the size of a dime," but agreed that the latest surgery had been blow.

"Physically I'm all right [but] I'm a little dejected. I've been pretty upbeat about the whole thing ... until that happened. That just kind of took the wind out of my sails a little bit."

Before the latest operation, Stewart had been undergoing physical therapy three days a week for approximately 90 minutes each day, and had progressed to the point that he could walk short distances without the aid of crutches. Following the latest operation, he was hopeful of resuming his rehabilitation at the end of this week and insisted that he is still on track to be back in the car for the season-opening Daytona 500.

Stewart was even present at Charlotte Motor Speedway for Saturday night's Sprint Cup Car, albeit watching from a vantage point over turn 1 located outside the track itself, rather than being able to join in down on pit road.

"You miss everything," he lamented. "The good thing is I've been able to go back to the track, been able to see the officials, get to talk to my team. I haven't been able to be around them a lot, but I value the time I have had," he added. "It feels like a jail sentence to me. You just do your time. You don't know when you're going to get out but you know you're going to get out eventually."

Stewart is also missing out on all the frantic activity at the Stewart-Haas Racing headquarters in Kannapolis, which currently is flat-out making preparations for the arrival of Kevin Harvick and Kurt Busch and the expansion of the tea to a four-car line-up for 2014, all the while trying to ensure that current driver Ryan Newman gets all the support he needs in this year's Chase.

"It's chaos right now," Stewart said. "You look at it on paper and it's supposed to work. But it's a long process ... We're knocking walls down and building race cars and we've still got three teams to finish the year with. It's a lot to wrap your arms around!"