Tony Thompson, 40, is clearly much leaner than when he faced Wladimir Klitschko nearly four years ago. (Katherine Frey/THE WASHINGTON POST)

District boxer Tony Thompson knew full well the last time he fought Wladimir Klitschko to be wary of his opponent’s lethal right hand. It was and continues to be the heavyweight champion’s signature punch, and Barry Hunter, Thompson’s sage trainer, had counseled his fighter repeatedly about how Klitschko could end the bout suddenly by landing it.

After lasting into the 11th round, Thompson tried to connect with a left cross, leaving his left side open. Klitschko struck immediately and forcefully to the jaw, and with 1 minute 38 seconds left in the round, Thompson collapsed to the canvas.

“You’d be an absolute idiot to stay in a straight line with him,” Thompson said after a workout on Monday afternoon at Headbangers gym in Southeast. “And that’s exactly what I was. I was an idiot.”

Nearly four years removed from that defeat in Hamburg, Thompson gets a rematch with Klitschko (57-3, 50 knockouts) on July 7 for the unified heavyweight championship of the world. The fight will take place in Berne, Switzerland, and even though Thompson, 40, is at an advanced age for a boxer, he has fought just five times since losing to Klitschko, now 36.

That abridged schedule means Thompson (36-2, 24 knockouts) has absorbed less punishment than the typical fighter, especially given that only one of those bouts lasted beyond the fifth round. He’s also clearly much leaner than the last time he faced Klitschko, who is a 50-1 betting favorite in the rematch.

Thompson made sure to illustrate just how much more endurance and pep he has this time by working the speed bag and jumping rope with pace during his open workout that included support from undefeated Brandywine heavyweight Seth Mitchell, who also has aspirations of fighting the 6-foot-6 Klitschko.

Entering his first fight against Klitschko, Thompson’s conditioning suffered because of a sore knee. Thompson said he was unsure of the exact nature of the injury but elected to keep it from his team, and it wasn’t until during the bout Hunter learned his fighter was weakened.

Subsequent medical examinations revealed Thompson had a torn meniscus.

“You wouldn’t see me jumping rope. You wouldn’t see me bouncing around,” the 6-5 Thompson said of his training regimen before the first fight. “As a fighter, you’re taught to train through and run through those things. It was a mistake.”

Better physical conditioning accounts for only part of why Thompson is taking a fearless approach to the scheduled 12-round fight at Stade de Suisse, the second largest soccer stadium in Switzerland. Thompson said he’s in a more comfortable place mentally and well aware this most likely will be his last chance to win the heavyweight title.

So Thompson is going to be particularly mindful of Klitschko’s right hand, which has ended three of his last four fights via knockout.

“The name of this game isn’t, ‘Knock you out,’ ” Hunter said. “If it happens, it happens. This is a boxing game. This game is not won on physical capability a lot of times but based on intelligence. We have to be smarter this time.”