"I just saw him walking through the garage," Johnson said. "The guy clearly is in pain. It will be interesting to see how he does."
Hamlin is trying to race this weekend on one good leg. And he doesn't know whether he can do it.
"I don't know how far I can go," Hamlin said after practice Friday. "It aches quite a bit, and the range of motion is a problem. If I had to do it today, there is no way I could do it."
Hamlin underwent ACL surgery on his left knee just nine days ago. Driving a race car isn't usually an option for a guy who just had a cadaver ligament placed in his knee.
It's not open-heart surgery, but it's not getting a tooth pulled, either. It's a big deal.
NFL players miss entire seasons after an ACL procedure. Tiger Woods didn't play in a tournament for seven months after his ACL surgery in June 2008.
Granted, Hamlin isn't running on a football field or playing 18 holes of golf, but he is trying to control a 3,400-pound machine at more than 130 mph.
"I hope it doesn't give out with me in front of him," Clint Bowyer said about Hamlin's knee. "We'll have to see how he'll be able to hang on. He's a tough kid. He'll be all right."
A driver racing with an injury is nothing new. Drivers don't have a choice. You get in the car or give up any chance of competing for a championship. NASCAR rules state a driver must start the event to earn the points for that race.
However, the Chase format makes it a little easier to give up your seat during a race. As long as a driver stays in the top 12, he's in the 10-race playoff.
But Hamlin isn't in the top 12 after the first six races, not even with his victory at Martinsville two days before the surgery. He ranks 15th, 24 points behind 12th-place Brian Vickers.
That rule on needing to start the race for points is debated whenever a driver finds himself in a situation like the one Hamlin is in now. Should the rules include a mulligan of sorts, allowing a substitute driver for one or two races to earn points for an injured racer?
That's not the case, so a guy has to man up and race in pain. Some of the stories are legendary, such as when Ricky Rudd taped his swollen eyelids open to see the track.
"Driving injured is part of the sport," Jeff Burton said. "But drivers don't like for people to know, the same way as other pro athletes. You don't want to be viewed as having a weakness. A lot of the times no one knows about it, but that wasn't an option for Denny."
Everyone knows, and everyone is watching to see what he can or can't do with a painful left leg that has limited mobility.
Mike Ford, crew chief for the No. 11 Toyota Hamlin drives, said the team made pedal adjustments to help Hamlin. Pushing the brake pedal was causing too much stress on Hamlin's knee, so the pedal assembly was changed to make it easier to apply.
Hamlin is not a right-foot braker, but he might try it some this weekend on the 1-mile oval at Phoenix International Raceway. Hamlin will have to use his left leg when he exits pit road, though.
Casey Mears is standing by if Hamlin can't go the 375-lap distance. Mears drove the car for part of the first practice session when Hamlin got out after 22 laps.
"I wanted to save as much energy and as much strength as I could," Hamlin said.
Ford also wanted to make sure Mears was comfortable in the car if the team needs to make the change during the race.
Hamlin did 52 laps in the afternoon practice but went back to the garage in the middle of the session and iced his knee in the car while the crew made adjustments. He went backward on the speed chart toward the end of practice.
The longer he raced, the tougher it got. Getting in and out of the car was handled gingerly. Bending the knee much is not an option. Every move looks painful.
But Hamlin is here to race, and Johnson understands. Johnson said no driver ever wants to get out of his race car.
"I can only imagine what it's like to watch your car on the track and you're not in it," Johnson said. "It's got to be the most difficult thing. You don't want to see anyone else in your car."
Burton said he has raced with broken ribs, a broken leg and even a broken back many years ago in his local-track days in Virginia. He said he had vertigo once about 10 years ago while racing in Cup for Jack Roush.
"I just couldn't do it," Burton said. "I had to get out of the car. We tend to get in the car sometimes when we probably shouldn't."
Phoenix normally is one of Hamlin's best tracks. He has five top-5s in nine starts. But he has never done it with this handicap. And he'll have to race an additional 63 laps. The event was lengthened this year.
Fatigue could become a factor for Hamlin late in the race.
"I don't have any concerns," Burton said. "Denny will know his limitations."
Jeff Gordon said he has one issue with Hamlin racing: "I'm just concerned that he's still going to beat me."
Terry Blount is a senior writer for ESPN.com. He is the author of "The Blount Report: NASCAR's Most Overrated and Underrated Drivers, Cars, Teams, and Tracks." He can be reached at email@example.com.