Katie Ledecky developed the "gallop" in her stroke with former coach Yuri Suguiyama. It gives her an advantage in the pool over her female competitors since most do not have the strength to sustain it. (Jayne Orenstein/The Washington Post)

Katie Ledecky is a world-class freestyler at 100 meters; she anchored the U.S. women’s 4x100 free relay to the silver medal on the first night of the 2016 Rio de Janeiro Olympics. She is the best female in the world at 200 meters, having won Olympic gold, and the best in history at 400, with an additional gold plus a new world record this week. But those were mere warmups for the 800 free, an event in which Ledecky is so dominant and so peerless that she nearly breaks the sport of swimming.

Much as Barry Bonds in his prime shattered the statistical norms that governed baseball — his on-base percentage of .609 in 2004 essentially inverted the rate at which the best hitters in the game make outs — Ledecky swims a different race than any of her competitors and has altered the very notion of what is humanly possible in the pool.

She zigs while everyone else zags. If you suddenly looked up and saw the field of swimmers midway through one of her 800s, you wouldn’t know whether Ledecky, often going in the opposite direction of everyone else, had been lapped or was the one doing the lapping. A good rule of thumb: It is the latter. She is essentially a sprinter in a pool full of distance swimmers, except she keeps sprinting the entire race — as if Usain Bolt ran the marathon the same way he runs the 100.

Ledecky’s world record time of 8:06.68 from Austin in January — a mark that could very well fall in Friday night’s 800 final, given the peak form she has demonstrated this week — is more than 11 seconds, or almost half a pool-length, better than anyone else in the world this year and more than seven seconds better than anyone in history.

In Thursday’s preliminary heat of the 800, Ledecky essentially coasted — swimming without kicking her legs for most of the race — and still put up the eighth-best time in history, an Olympic-record 8:12.86, to win her heat by more than 6½ seconds. She now owns the 12 fastest times in history.

A victory Friday night, in a race in which victory for her is a foregone conclusion, would complete a sweep of the 200, 400 and 800 freestyles, something only one other swimmer in history, Debbie Meyer in 1968, has pulled off. When added to her gold in the 4x200 free relay, it also would make Ledecky just the third American female swimmer, after Amy Van Dyken in 1996 and Missy Franklin in 2012, to win four golds in a single Olympics.

She is often compared to her U.S. teammate Michael Phelps, the most decorated Olympian ever and the last person to have dominated the sport in such a fashion. But even Phelps, whose best races come at shorter distances, never destroyed the competition the way Ledecky does at her longer ones. In a sport measured in hundredths of seconds, Ledecky is often left hanging on the wall for a half-minute or longer for everyone else to finish before climbing out.

“Even in Michael’s heyday, I’ve never seen such dominance, from the clock standpoint, as Katie has,” three-time Olympic gold medalist and current NBC commentator Rowdy Gaines said. “I’m at a loss for words sometimes.”

Leah Smith, another American and the fourth-place qualifier in Thursday’s heats, recalled swimming against Ledecky in Austin in January and hearing the public-address announcer blurt out the new world record just as Ledecky touched the wall.

“I had just flipped for my last 50,” Smith said, “and I kind of was like, ‘Well, this probably isn’t a good race for me, just doing the math.’ ”

Janet Evans’s 1989 world record in the 800 of 8:16.22 stood for 19 years until Great Britain’s Rebecca Adlington broke it with an 8:14.10 at the 2008 Beijing Olympics, and it would be another five years until Ledecky, then 16 years old, took Adlington’s mark down with an 8:13.86 at the 2013 world championships in Barcelona. Ledecky has broken her own mark three times since then; her current mark of 8:06.68 would have stood as the world record for men as recently as 1976.

“She’s blazing a completely differently trail than anyone who’s ever done it,” USA Swimming national team director Frank Busch said.

To adapt Bobby Jones’s famous quote about Jack Nicklaus, Ledecky swims a race with which no one else in the world is familiar.

At that most recent world record 800 swim in Austin — a race she won by more than 17 seconds — her average 50-meter lap clocked in at 30.42. To put that into perspective, just three other women in Tuesday night’s final of the Olympic 400 free — a race of half the distance, featuring the best middle-distance freestylers in the world at their peak form — maintained that pace or better.

In Austin, Ledecky’s 16th and final lap of her 800 was a staggering 28.84. How fast was that? Not a single competitor in the finals of this week’s 400 free or 200 free — including, curiously, Ledecky herself — swam a closing lap that fast.

She never reveals her goals, not even to her family, until she hits them, but there is reason to think she has a frighteningly low time in mind for Friday night. When she was asked before the meet began whether a time of 8 minutes flat was possible, she laughed at first, then ultimately refused to rule it out.

“Eight minutes is not my goal — I think that’s pretty easy to say at this point,” she said. “That would be a pretty big drop. But I still believe anything is possible.”

The 800 is the race that delivered Ledecky’s international breakthrough at the 2012 London Olympics. A nervous kid of 15, she swam an 8:23.84 in the preliminary heat, the third-fastest time in qualifying. The next night, she stunned the world with an 8:14.63, winning by more than four seconds and earning her first Olympic gold medal. She still has yet to lose an individual final at a major international meet — a perfect 14 for 14.

A similar improvement from prelims to final here would put her at 8:03.65 on Friday night — a 13th career world record, a fifth Olympic gold, another zig in a pool full of zags.