"I'm playing injury free. I'm not injured. My quick twitch is back. My speed is back, my strength is back," James said after the Lakers' 103-96 win over the San Antonio Spurs on Sunday.
After giving up 112 points and allowing the Los Angeles Clippers to shoot 51.9 percent in an opening night loss, the Lakers have won five games in a row, limiting their opponents to an average of 96.8 points on 38.1 percent shooting.
James, who turns 35 next month and is playing in his 17th season, said the groin injury he suffered on Christmas Day made his defense worse than what he is capable of delivering.
"Playing with a torn groin last year -- even when I came back it was still partially torn -- it was difficult to be able to move and shift like I'm capable of doing that defensively," James said. "For me, I just take the challenge. I love being challenged. Coach [Frank Vogel] challenged me, AD [Anthony Davis] challenged me, I challenged myself.
"I put a lot of hard work into my offseason by getting my quick twitch, getting my bounce back, getting my speed back, my reaction time back. My mind has always been there. That's what it's all about."
The numbers support what James is saying. He is contesting 70% of attempts against him, up from 54% last season, according to research by ESPN Stats & Info. He's also keeping offensive players farther away from the hoop: Through the first six games, the average field goal attempt against him is from 17.6 feet, compared to 15.6 feet last season.
And while opponents are shooting an identical 37% from the field with James as the primary defender, just as they did last season, his points allowed per play as the primary defender has dipped from 0.80 last year to 0.77 through the first two weeks of the season.
"Well, it's contagious, and his commitment on that end of the floor has been a great surprise for us in terms of just how proficient he's been," Vogel said of James' impact in the win over the Spurs in which L.A. limited San Antonio to 39.8% shooting (including just 24% from 3). "He's leading the charge with care factor on that end of the floor. When he's working that hard and caring that much about getting stops, it carries over to everybody else, and you see it on the floor."
While James has impressed with his defensive commitment -- he has drawn four charges through the first six games, according to Second Spectrum data, which ties him for fourth in the league, as opposed to his eight charges drawn in 55 games last season -- he's far from the only Laker consistently making stops.
Davis, who leads the league in blocks, had four more against the Spurs.
"Obviously we still have a lot to work on offensively, but we try to make sure that we strive on defense every game," Davis said. "We want to be the best defensive team in the league, and we'll be tough to beat."
Dwight Howard, a three-time Defensive Player of the Year award winner, had another strong game on the defensive (and offensive) end, contributing two blocks, 13 rebounds and 14 points on 7-for-7 shooting off the bench, plus a timely strip of Rudy Gay late in the fourth when the Spurs were making a run.
"I don't see it as a role, I see it as my purpose," Howard said. "I think it's my purpose to go out every single night and play hard defense, trying to block every shot, trying to be in the paint, get a lot of steals, go for loose balls. Whatever I can do for this team, be of service, that's my mission. I don't see it as my role, I see it as a purpose."
L.A.'s front office put a premium on defense with its offseason moves, bringing in shot-blockers like Howard and JaVale McGee and wings with All-Defensive Team credentials on their résumés in Avery Bradley and Danny Green. Bradley, who left the game early after getting kicked near his right knee, had a steal and chased Dejounte Murray around before exiting. He is considered day-to-day after X-rays came back negative.
Vogel says the Lakers still "have a long way to go" in order to become the defensive force he hopes to see, but they have certainly already shown that taking pride in defense will be a part of their identity this season.
"All of us, all of us, with LeBron and AD being the leaders of the team, it starts with them," Howard said. "The first guys on the court it starts with them. The second unit, the Bad News Bears -- not the Bad News Bears in a bad way, but they're going to bring bad news to the other team. That type of bad news. But we come out and you play that hard, tough-nosed defense, it makes it tough for teams to score, then they've got to deal with our first unit again."