Former heavyweight champion Wladimir Klitschko is philosophical about his 2016 in which he did not fight because twice he had his rematch with lineal champion Tyson Fury called off due to Fury's personal problems and failed drug tests.

It led to what will be a 17-month layoff for Klitschko, the longest of his decorated 21-year professional career. He has had two heavyweight world title reigns, the most recent one ending against Fury by unanimous decision in a dreadful November 2015 fight in which Klitschko looked as bad as he ever has.

"Without losing my last fight to Fury I wouldn't be able to make this fight with Anthony Joshua. Things happen for a reason. Now we have this huge fight -- 90,000 people are coming. I have fought in sold-out stadiums in front of 65,000. I've done that a few times. But 90,000?" Wladimir Klitschko

But now Klitschko (64-4, 54 KOs) sounds like he has a new spring in his step as he prepares for perhaps the biggest fight of his career when he challenges young and powerful British star Anthony Joshua (18-0, 18 KOs) for his heavyweight world title on April 29 at Wembley Stadium in London, where a British-record crowd of some 90,000 is expected.

It's such an enormous fight that it could shatter British pay-per-view records on Sky Box Office and American networks Showtime, with ties to Joshua, and HBO, with a long relationship with Klitschko, which are locked in a bidding war to secure American television rights. It may be the biggest heavyweight fight since the 2002 showdown between then champion Lennox Lewis and former champ Mike Tyson.

Heavyweight titleholder Anthony Joshua, left, and former champ Wladimir Klitschko have mutual respect for each other entering their showdown in London on April 29. Richard Drew/AP

Klitschko, who will turn 41 the month before the fight, will be trying to regain one of the belts he lost to Fury (who was stripped of it 10 days after beating Klitschko) as well as show that the defeat was nothing more than a blip on the radar for a man who has made considerable heavyweight history, having had his second title reign past 9½ years (second longest in division history) through 18 title defenses (third most in division history and as many defenses as Joshua has fights). When he steps into the ring with the 27-year-old Joshua, Klitschko will extend his division record with a 29th world heavyweight title fight appearance.

With the end of his long layoff close and training camp due to begin soon, Ukraine's Klitschko is anxious to get started. He said he has put the disappointment of 2016 behind him. He said ultimately that while his year was a bust professionally, it was at least rewarding personally.

"I enjoyed my time off. It was the first time in 26 years (including amateur boxing) I had such a long layoff," Klitschko told ESPN in a telephone interview Monday, after he and Joshua met the media for a joint news conference at Madison Square Garden in New York. "Through all those years I was always training and getting ready. Then, boom, one-year and longer break. But I enjoyed it. Boxing is my life but my life is not only boxing. So I had my adventures. I had things to do with my Klitschko foundation, many things to do."

"This is a defining fight, everything I dreamed of. He's still here. This is my time to put him out. Put him out for good. It's his decision on when to retire but I can cause a massive impact on what he decides to do." Anthony Joshua

Klitschko said he also enjoyed spending time with his daughter Kaya, whom he had in 2015 with actress Hayden Panettiere.

"And I was also training," Klitschko said. "It wasn't like I was sitting on the couch drinking beer and watching other fights."

The one thing Klitschko wanted to do in 2016 was compete in the Rio de Janeiro Olympics in August. He won the super heavyweight gold medal in 1996, as did Joshua in 2012, and wanted to go for gold again now that professionals were allowed to compete for the first time.

However, Klitschko did not get the opportunity because the Fury fight was still on the schedule for September and contractually he was not allowed to participate in any interim bouts. So when Fury pulled out, it left Klitschko disappointed that the fight fell through in addition to losing the chance to go for Olympic gold again. But Klitschko said he has found a silver lining.

Wladimir Klitschko, left, lost his titles to Tyson Fury in 2015, but he's ready to regain one of them against Anthony Joshua on April 29. Sascha Steinbach/Getty Images

"Without losing my last fight to Fury I wouldn't be able to make this fight with Anthony Joshua," he said. "Things happen for a reason. Now we have this huge fight -- 90,000 people are coming. I have fought in sold-out stadiums in front of 65,000. I've done that a few times. But 90,000? Never something that huge and I am excited about it and looking forward to it."

Asked about his feeling toward Fury, Klitschko, ever the gentleman, nonetheless declined to discuss him in any detail.

"I don't even want to waste your time or mine and give any comments on him," he said. "What we cannot change I just forget about. It's done. I'm just moving forward. I'm not looking back."

OK, so what the heck happened in that fight?

"I'm not going to go through the reasons of why and how," Klitschko said. "It has always been in sports like that. There are always bumps in the road. I've had my bumps in the road. Now my motivation is as high as it's ever been before. I learned a lot from this. Whatever it was I will not take away credit from Fury. He was better that night. I couldn't make it better with a rematch because it was canceled. It is what it is."

Joshua once served as a Klitschko sparring partner in 2014 when he was getting ready for a defense against Kubrat Pulev, a fight that ended in the fifth round with the knockout of the year. It was in that camp that Joshua and Klitschko developed a friendship and respect for each other. You won't see or hear any trash talking from them in the buildup to the fight. Joshua is the anti-Fury.

But Joshua also views the fight as a passing of the torch bout, sort of like when a young Larry Holmes brutalized an aging Muhammad Ali and then the young lion Tyson smashed the remnants of Holmes.

Anthony Joshua, right, demolished Eric Molina in December to defend his heavyweight world title. Andrew Couldridge/Reuters

"That's the way things go," Joshua said. "This is why I can't wait. This is a defining fight, everything I dreamed of. He's still here. This is my time to put him out. Put him out for good. It's his decision on when to retire but I can cause a massive impact on what he decides to do."

Klitschko has a decidedly different view of the fight, saying it is happening at the right time.

"Some say this fight is too late for me, too soon for him, but it's perfect," Klitschko said. "In three years I will be too old and he will be too good, so the timing is perfect."

As for Joshua's notion of the fight being the heavyweight passing of the torch a la Holmes-Ali and then Tyson-Holmes, Klitschko begs to differ.

"(Joshua promoter) Eddie Hearn says it will be a very painful night for Klitschko but how is (Joshua) going to react under the pressure," Klitschko said before deflecting the examples of older fighters losing to the young guns.

He cited the aging Ali's huge upset of the younger George Foreman in the 1974 "Rumble in the Jungle" as well as Foreman's historic knockout upset of young Michael Moorer to regain the heavyweight title 20 years later. And there is also an example in Klitschko's own family, when older brother Vitali Klitschko came out of a nearly four-year retirement and laid a beating on younger Samuel Peter to regain a heavyweight title in 2008.

Still, there will be questions about what Wladimir Klitschko has left given his age, the long layoff and the horrible showing against Fury.

"All those questions will be answered on April 29. Do I still got it or is it too late? I'm looking forward to his challenge," Klitschko said. "I have my goal to become three-time world champion and I'm obsessed with it."