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.

Also Friday, Toronto’s Josh Liendo and Montreal’s Ilya Kharun booked spots in the men’s 100-metre butterfly final Saturday. The two shared the Olympic podium in Paris last year, with Liendo taking silver and Kharun the bronze. Liendo turned in the second-fastest time in the semifinals of 50.24 seconds, while Kharun was fourth in 50.39.

At this week’s world championships in Singapore, Ledecky and McIntosh will renew a rivalry that captivated the Olympics last summer.

McIntosh also joins the Canadian history books as one of just three swimmers from Canada to achieve double gold at the Olympics and the only female.