In the fourth quarter of a playoff game against the Boston Celtics in 2008, LeBron James came off a screen and rumbled to the basket and challenged Kevin Garnett at the rim.

Garnett shoved him in the midsection as he went airborne, knocking James back slightly, but he reacted by just reaching farther and then threw down a statement dunk that effectively ended the game.

“LeBron James with no regard for human life!” TNT announcer Kevin Harlan exclaimed at that moment, officially branding the dunk.

It is one of the signature athletic plays of James’ career, a pure power move that came in a halfcourt set in which the entire defense was aligned to stop him and couldn’t. If you search YouTube for clips from the mid-2000s you will see plenty of this from James, beating three opponents in one move and embarrassing a help defender who tried to stop him at the rim.

That was then, and this is now. James is a few days away from his 30th birthday, and his legs aren’t the same ones that could spring over Garnett six years ago. James recently played his 40,000th career NBA minute, including playoffs. Before he turns 30 on Dec. 30, James will have played more minutes than Larry Bird did in his entire career.

So it should not come as a surprise that James is starting to show his odometer. The numbers and the eye test show this season that James has perhaps lost a half step. And when sampling the past highlights, the difference becomes more pronounced.

The Cavs have been thrilled with James’ return on every level. He’s been everything to them they hoped he would be from on-court leader to locker room voice to business generator. But team officials have also noticed James is not as electric athletically as they were expecting, especially after offseason weight loss might’ve refreshed him.

“The LeBron who could dunk on any player at any time is probably gone,” said one league advance scout. “He’s probably never been a better basketball player than he is right now, though.”

League executives and scouts are seeing James not look as bouncy and athletic this season compared to recent years. They especially point to his field-goal percentage, which has alarmingly dropped 10 percent from last season.

In one of the more remarkable stats of James’ career, he has increased his field-goal percentage for seven consecutive seasons, which is an unheard-of run for a perimeter-based player. Had James made seven more field goals in the 2006-07 season, that run of increases would’ve been 10 consecutive years.

“

The LeBron who could dunk on any player at any time is probably gone. He’s probably never been a better basketball player than he is right now, though.

“ — NBA advance scout

But many league observers believe any physical slippage James may be dealing with is not holding him or the Cavs back as their current eight-game win streak attests.

“There is no way to compare what LeBron is doing this season to what he did in the last few years,” said one league executive. “He’s dealing with a completely different roster that is requiring him to play a different style. He’s working harder on offense because he’s playing point guard almost every minute he’s on the floor. … The Heat had mastered the art of creating space and there were way more driving lanes than he typically has now.”

As for James himself, he dealt with some back issues earlier in the season but is not believed to be battling any serious injuries. When asked, he’s given a standard answer about his overall health by repeatedly saying, “I’m active.”

“Five years ago he was more likely to look at the defense and just attack it by himself and then react to what they did,” one Eastern Conference assistant coach said. “Now, you’ll see him set the defense up and take advantage of its weaknesses. If that means fewer dunks but more efficient shots for himself or his teammates then you could say he’s playing better offensively now than he was then.”

James has taken a balanced approach to the season, at times playing an energy-zapping aggressor role and at other times easing back to let his generally deep team share the burden. He was the catalyst in taking over the ballhandling duties after the Cavs’ 1-3 start. They are 12-4 since with his assists jumping but his scoring taking a dip from his usual levels.

Various all-encompassing stats such as real plus-minus and PER have recorded this as James regressing. The Cavs’ record over the last month tells a bit of a different tale.

“There is indeed something that has regressed this season involving LeBron, I will say that,” a league scout said. “The Heat.”