"He had some discomfort since Thursday night, and had been working on it trying to get it fixed up. We hadn’t put much thought into it, to be honest with you, and then after the first run (Saturday) we talked about how it was pretty detrimental physically for him to continue practice," crew chief Alan Gustafson said. "Fortunately, the guys did a great job on the car, and I don’t think there was much we were going to learn anyway. We’ve been here for a long time, got a good idea on what we need to race with. Glad the car was good, and made the decision pretty easy."

Gordon has battled back issues before, particularly in 2009 in the wake of a vicious accident on the road course at Watkins Glen International, and at one point the discomfort had him concerned for his career. But the 42-year-old has been feeling much better in recent years, and was enjoying a strong 2014 campaign that saw him win at Kansas Speedway two weeks ago and lead the Sprint Cup points for nearly two months. Gordon is in the care of Dr. Jerry Petty, a Charlotte-area neurosurgeon and spinal specialist who has worked with many NASCAR drivers.

"It’s unfortunate," Gordon said. "I’ve had some spasms in the past, but this one is a little bit different. And so, I just want to really be cautious and take care of it. It doesn’t do me any good to be in the car right now, especially when the car is as good as it is. It’s really about getting prepared for 600 miles tomorrow. I have no doubts that I can be in this car and be competitive tomorrow if I just take it easy over the next 24 hours.”

"This is something that he’s had before, that he has some experience with," Gustafson added. "He knew Thursday night — unfortunately, it was a familiar feeling — that this was not good, and he needs to do everything he can. He did all he could as far as treatment and rest and whatever’s required in hopes that today would be good to go. And I felt like today he thought he was going to be. But unfortunately, getting back in the car triggered discomfort."

This weekend brings the 20th anniversary of Gordon’s first victory at NASCAR’s top level, which came at Charlotte in 1994. His former crew chief Ray Evernham said Gordon is underrated for his toughness, which has helped to sustain the driver’s consecutive-start streak even during episodes of physical duress.

"We won one of the Southern 500s that we won — and we won four of them in a row — one of them, he’s throwing up in the car halfway. I’ve seen him drive oval races like Darlington sick, when it was 500 miles and Labor Day weekend and 120 degrees in the car, and I’ve also seen him finish road races with holes through the layers of skin. Through his glove, through his skin, just holes in his hand," said Evernham, now an advisor with Hendrick.

"His toughness is underrated. You don’t win 89 races and be in this sport 20 years without missing a race, knock on wood, without being trough. He’s not felt good, and there’s been times he’s been hurt in that car. But to me, I still say you have to keep an eye on the 24 (car) tomorrow night."

Gustafson said Gordon’s race victory at Kansas, which likely assures the driver a berth in the Chase for the NASCAR Sprint Cup regardless of Sunday’s outcome, won’t figure into any decision as to whether he starts the 600. Smith tested Gordon’s car at Charlotte in January, so Gustafson said the team has a baseline setup for the standby driver in the event he is required to take over the vehicle.

Smith said he found out about the potential relief duty Saturday morning. Team officials indicated that there were no plans for Smith to drive the No. 24 car in final Sprint Cup practice, but that he would sit in the car to get his bearings in case he were needed.

"I’ve tested with those guys on quite a few different occasions over the offseason, and I told them whatever they need, I’m there for them," Smith said after Coors Light Pole Qualifying for the Nationwide Series. "Obviously, it’s a great race car, great team and the main thing is going to be Jeff making sure he’s healthy for whatever he needs to do the rest of the year."

But the plan remains for Gordon to be behind the wheel. "Our plan right now is for Jeff to come here, get in the car, start the 600 and finish it and win it. That’s what we’re going to try to do," the crew chief said.

"I think he’s extremely tough, and he’s extremely dedicated. He’s very competitive, and it’s difficult anytime to not be able to do your job based on physical requirements or something that’s personal. And I know that’s not easy for him, but I know tomorrow he’ll do anything he can to get it in go. These guys go through a lot physically, and he’s done it over a long period of time. His body’s taken a toll. It’s amazing that he’s in as good a shape as he’s in, and is in good a condition as he’s in week in and week out, and I’m sure he’ll fight through this the best he can."

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