LONDON >> At 7:30 p.m. Saturday night, London time, Michael Phelps, barring disaster in the morning heats, will step atop a starting block at the Olympics Aquatic Centre for the Olympic Games 400-meter individual medley final.

Four years ago, Phelps dove into the 400 IM final, chasing a ghost through the uncharted waters of Beijing. Tonight, a very real and familiar rival will stand at the ready only a few feet away.

Like Phelps, Ryan Lochte has tried to downplay a rivalry which there is no denying.

“Michael’s just one person,” Lochte said. “There’s a bunch of other swimmers across the world that I have to worry about.”

In reality, the rest of the 400 IM field will be mere extras in the opening act of the Games’ epic production, a race that promises to electrify the London Olympics on their first night of competition.

Lochte and Phelps, both 27, will also meet in the 200 IM on Thursday, the second race in a showdown four years in the making, and that promises to leave the rest of swimming competition and the opening week of the London Games in its wake.

“We’re looking forward to watching Ryan and Michael duke it out,” said U.S. swimmer Natalie Coughlin, an 11-time Olympic medalist. “I think that will be an awesome race and it will have a lot of energy behind it.”

For Lochte, who will swim six events, the Games will be the defining moment for an athlete whose pursuit of Phelps began almost the moment he climbed out of the pool the final time in Beijing. Phelps will compete in seven events, one fewer than 2008 when he won a record eight gold medals, eclipsing Mark Spitz’s seven golds from 1972. With 16 Olympic medals, Phelps is just three shy of surpassing Soviet gymnast Larisa Latynina as the all-time Olympic medal leader. But just as he refused to be defined by his pursuit of Spitz, Phelps resists being measured against Lochte, Latynina or even his 2008 record-shattering performance.

“I want to be the first Michael Phelps,” he said. “That’s what I’ve always wanted to do.”

Instead, Phelps views London as an opportunity to leave on his own terms a sport he has dominated for more than a decade.

“I think going into Beijing we were trying to conquer everything. Bob and I have been a lot more relaxed over the last four years,” Phelps said, referring to longtime Coach Bob Bowman. “We’re having fun. This is the closure. It’s really how many toppings do I want to have on my sundae? I’m having fun. That’s what I’m doing. I’m having fun.”

Phelps, however, hasn’t always enjoyed swimming after his Beijing triumph.

“I think really after 2008, I just didn’t want to do it,” Phelps said. “I just didn’t want to put in the work. There were times where I just wouldn’t come to practice. It didn’t excite me.”

Phelps was largely AWOL from the pool in North Baltimore, Md., periodically popping up in Las Vegas or celebrity golf tournaments. Or on the pages of a News of the World, a London tabloid in photos of him holding a bong at a post-Olympic party in South Carolina.

Phelps’ lack of commitment put a strain on an already volatile relationship with Bowman.

“I was clearly frustrated for a couple of years there because I’m the kind of person who wants to be as prepared as you can possibly be,” Bowman said. “I wanted Michael to have as much training a day as possible so we can overcome things that may come up down the road and when we didn’t do that, you know, that’s tough on me.”

Eventually Phelps, with help of close friend Baltimore Ravens linebacker Ray Lewis, regained his focus.

“I was just going through the motions. 2008, 2009, that’s how I was, 2010 that’s kind of how I was,” Phelps said. “In the latter part of 2010 I kind started showing more interest. It was really all about me being able to find the passion again.”

It’s no coincidence that spark came after Lochte beat Phelps in the 200 IM for the first time at the 2010 U.S. championships.

While Phelps wavered after Beijing, Lochte had already zeroed in on London. He upped both the quantity and quality of his workouts and then supplemented his training with regimen of Strongman competition workouts, throwing oversized tires and pulling heavy chains between swim sessions.

“I can tell you no other swimmer in the world is doing what I’m doing,” said Lochte, who trains in Gainesville, Fla., under University of Florida coach Gregg Troy.

Phelps at times has seemed dismissive of Lochte’s unorthodox methods.

“I think everybody needs something different,” Phelps said. “For Ryan it might be throwing a tire. For me I don’t see myself throwing a tire or lifting chains or any of that.”

Yet the regimen continued to pay off for Lochte. He beat Phelps in both the 200 freestyle and the 200 IM at the 2011 World Championships, in the latter setting swimming’s first world record since FINA, the sport’s worldwide governing body, banned high tech suits in 2010.

Lochte knocked off Phelps in the 400 IM at the U.S. Olympic Trials last month in Omaha, Neb. Phelps came back to edge Lochte in the 200 freestyle and 200 IM by a combined total of 14-hundreths of a second.

“I’m not going for the silver or bronze. I’m going for the gold,” Lochte said. “That was just a little appetizer. This is the big show. This is what I’ve been working for.

“Right after Beijing I had a four-year plan to get here. This was going to be my year. This is the year I put everything into.”

And the plan doesn’t include Phelps.

“If Michael’s right there with me,” Lochte said with a shrug. “He’s right there with me.”

Troy, sitting nearby, laughed.

“He doesn’t need to worry,” Troy said. “Michael will be right there.”