Rescue workers tend to the wreckage of Denny Hamlin after he collided with Joey Logano last month. Some say it was payback for a block Hamlin put on Logano the previous week. (Reed Saxon/AP)

NASCAR’s grassroots popularity was fueled by the Richard Petty-Bobby Allison feuds of the 1970s and ’80s, followed by the showdowns between the menacing Dale Earnhardt and precocious Jeff Gordon in the 1990s.

But when riled stock-car racers retaliate with 3,000-pound cars on the track rather than with a well-placed punch or smart-mouthed insult off it, the stakes of NASCAR rivalries suddenly spike higher.

Denny Hamlin is the latest exhibit. Saturday’s race at Richmond International Raceway will mark the fourth consecutive that the Joe Gibbs Racing driver will miss after suffering a compression fracture in his back when Joey Logano sent his No. 11 Toyota headfirst into the wall at a March 24 race at California’s Auto Club Speedway.

The contact came during the last lap, when Logano threw a block that some viewed as within the bounds of good, hard racing. Others saw it as a reckless rebuttal to Hamlin’s block one week earlier at Bristol, which caused Logano to spin out.

Regardless, Hamlin’s back injury has drawn attention to the tricky issue of payback in motorsports. When racing at 200 mph, where exactly is the line between acceptable and unacceptable retribution?

“It’s a hard line to really find,” concedes Hamlin, 32, of Chesterfield, Va. “As athletes, we’re nearly barbarians in our outlook, in the sense that when we feel we’ve been done wrong, our immediate reaction is to get that guy back. But ultimately, in our sport, the risk for injury is a little more. . . . All you have to battle back with is your racecar, which is tough on the race teams [who have to repair the damage] and, sometimes, the drivers. It’s a different ballgame.”

It’s rare for NASCAR drivers to miss races because of injury. Despite near-weekly on-track scuffles and spectacular multi-car pileups, stock-car racers are pros at playing hurt — whether that means driving with a broken hand or ribs, postponing corrective surgery or, for much of the sport’s history, dismissing likely concussions as “getting one’s bell rung.” That tough-nosed approach is partly a result of the imperative to collect points toward qualifying for NASCAR’s season-ending 10-race championship competition. And it’s partly a testament to strides NASCAR has made in making its tracks and the racecars safer.

The latter is a particular point of pride at Joe Gibbs Racing, which hadn’t had a driver miss a NASCAR race because of injury for 22 years before Hamlin fractured his L1 vertebra in the wreck at California, aggravating a pre-existing bulging disk lower in his spine in the process.

Nonetheless, Hamlin insists he could tolerate the pain that would ensue during a 400-lap race Saturday at Richmond. The problem, in the view of his doctors, is the damage that another wreck could do to a vertebra that hasn’t healed sufficiently.

In a sense, helping Hamlin decide when to return to racing is familiar terrain for Gibbs, the Hall of Fame former coach of the Washington Redskins.

“There are two things you have to consider,” Gibbs said in a telephone interview. “One is, how does the athlete feel? I always told our football players: ‘I don’t want you out there unless you’re 100 percent. It’s a contact sport, and you’ve got to really want it and be champing at the bit. If you’re not, hold off because somebody else is probably going to do a better job than you.’ ”

After talking with Hamlin, Gibbs said he was convinced his driver was raring to strap in at Richmond, which is only about a 30-minute drive from Chesterfield.

But the other consideration, Gibbs noted, is what doctors advise. In Hamlin’s case, the neurosurgeon in charge didn’t clear him for Richmond, which comes four weeks into what was projected as a six-week recovery period.

The fact that Hamlin is tumbling in the points standings in the interim — he’s now 26th, down from 10th when the wreck occurred — doesn’t factor in the decision, Gibbs insisted.

“Denny is a big part of our team. We want him here for 15 years,” Gibbs said. “You’re not going to make a decision on points; you’re going to make a decision about what’s best for him.”

Said Hamlin, who was in Washington on Wednesday as part of an event held by the American Red Cross and FedEx, his team’s sponsor: “It’s a balance between risk and reward. Obviously there is no exact science to knowing when a bone is 100 percent healed. What are the odds of something catastrophic happening or just re-fracturing and having to start from scratch?”

As Hamlin wrestles with that weighty issue, his feud with Logano, a former teammate 10 years his junior, has had the effect of shifting the spotlight back to NASCAR drivers’ personalities — an element of the sport that has been overshadowed the last decade by contentious debates about racecar design and rulebook minutiae.

“The sport is personalities and drivers,” said third-generation racer Kyle Petty, 52, now an analyst with SPEED TV. “It’s not 3,000-plus-pound cars running 200 miles an hour. That’s part of the sport. But what makes fans identify with NASCAR is that driver. That’s the important part.”

Throughout NASCAR’s history, fans’ rooting interests have fallen along familiar fault lines: good vs. evil; wily veteran vs. cocky rookie; Ford driver vs. Chevy driver; and, the perennial favorite, self-made man vs. silver-spoon son of privilege.

Bobby Allison, from the steel-mill foothills of Hueytown, Ala., cast himself as the common man in his battles against NASCAR’s “King,” Richard Petty, who was flush with deep-pocketed corporate sponsors.

Three-time NASCAR champion Tony Stewart took a similar tack against Logano after the March 24 race at California, calling the 22-year-old “nothing but a little rich kid who has never had to work a day in his life.” Before knocking Hamlin into the wall, Logano had blocked Stewart on the final restart, relegating him to a 22nd-place finish.

The barrel-chested Stewart stormed over to Logano’s car afterward and shoved the youngster, who threw a water bottle at him.

The fracas paled in comparison to the nationally televised fistfight at the 1979 Daytona 500 between Cale Yarborough and both Allison brothers, Bobby and Donnie. But it was enough to spur Texas Motor Speedway President Eddie Gossage, a marketing master, into action.

He was so delighted by the post-race eruptions at California, which happened two weeks before NASCAR was scheduled to visit his Texas track, that he filmed a YouTube video called “Eddie’s Fight Club,” in which he asked a pro wrestler, MMA fighter and former NHL enforcer how to properly conduct oneself in a feud. Then he erected a boxing ring near Victory Lane, complete with stools, boxing gloves and towel in each corner, with a sign that read “For Post-Race Use Only.”

“When you look at feuds right now, everybody gets mad and they go to their Twitter,” Gossage said, lamenting the decline of face-to-face showdowns in the sport. “I don’t think Cale Yarborough and Bobby Allison would have thought that’s the way you solve those things.”

Note: Matt Kenseth, stripped of his pole award from last week at Kansas in a raft of penalties levied by NASCAR this week, set a track record with a lap at 130.334 mph in qualifying, the Associated Press reported. Kenseth, another member of Joe Gibbs Racing, edged teammate Brian Vickers by 0.005 of a second to claim only the 10th top starting position in 481 career starts. Jeff Gordon qualified third, followed by Kasey Kahne and Clint Bowyer.