Generational swimming talents Summer McIntosh and Katie Ledecky clash in Olympics preview

In one of the most consequential non-Olympic races in years, all-time swimming great Katie Ledecky could face an unprecedented challenge Saturday from Canadian teen Summer McIntosh.

In one of the most consequential non-Olympic races in years, all-time swimming great Katie Ledecky could face an unprecedented challenge Saturday from Canadian teen Summer McIntosh in an event the American has owned for more than a decade.

The pair will compete in the 800-meter freestyle final of the swimming world championships, in a race that'll be streamed live on Peacock at 8:21 p.m. local time in Singapore (8:21 a.m. ET)

"This will be the biggest race of this century, men or women, from outside of the Olympic format," three-time gold medalist and NBC swimming analyst Rowdy Gaines told NBC News. "I don't know how you can get bigger than this."

Gaines called the Ledecky the greatest female swimmer of all-time and McIntosh the best contemporary performer, saying both judgments are "not even close."

The 28-year-old Ledecky has 14 Olympic medals on her mantle at home, nine of them colored gold. McIntosh, 18, took home three golds and a silver from in Paris last year.