The world number one was knocked out in the second round of the Canadian Open

Defending champion Daniil Medvedev was sent crashing out of the Canadian Open by Nick Kyrgios as the Australian continued his impressive form in Montreal on Wednesday.

Fresh from winning a first ATP singles title in three years by claiming the Citi Open in Washington DC last weekend, Kyrgios picked up a major scalp as he fought back to defeat world number one Medvedev in three sets, 6-7(2), 6-4, 6-2.

Medvedev, 26, was entering the match on the back of his own title win at the Los Cabos Open in Mexico, but he came off second-best in a two-hour clash at the ATP Masters 1000 event.  

The defeat means Medvedev will see his lead at the top of the ATP ratings shrink when they are updated on Monday.

The Cincinnati Masters is up next, and while world number two Alexander Zverev remains sidelined with injury, number three Rafael Nadal has said he will return after skipping Canada as an injury precaution - marking a threat to Medvedev's status.

Kyrgios, meanwhile, has won 14 of his past 15 singles matches, with his sole defeat coming to Novak Djokovic in the Wimbledon final last month.

"I had a very clean objective of how I was going to play, a lot of serve-and-volley, a lot of aggressive play from the back," Kyrgios said of his win over Medvedev.

"I executed better than he did, that's all it comes down to. He won the first set and I feel like I had opportunities there as well, so hopefully I can just keep this rolling."

The Australian, 27, improved his head-to-head record against Medvedev to 3-1, as the Moscow-born star rued his missed opportunities.  

"For me, today the biggest difference was that I missed in some important moments some shots," Medvedev said.

"I didn't miss much, but missed just a few where I think it could be different maybe in the later stage of a tournament. That's a pity. At the same time, well, it's like this."

Kyrgios - so often prone to on-court outbursts - remained focused despite dropping the first set.

"He was great. He was playing good. He beat me fairly, if we can say like this," Medvedev added.

Medvedev's defeat was one of several shocks in Montreal as each of the top three seeds exited the tournament.

Second seed Carlos Alcaraz of Spain was dumped out by America's Tommy Paul, while third seed Stefanos Tsitsipas of Greece went down to British underdog Jack Draper.

That series of defeats makes it the first time a Masters 1000 event has seen the top three seeds all lose their opening matches since Indian Wells in 1999.

While Medvedev will turn his attentions to Cincinnati next week, the biggest target on the horizon remains the defense of his US Open title when the action begins in New York on August 29.