Nick Kyrgios says there's "no reason" he can't go into Wimbledon as a major title threat after fighting back from a set down against Andy Murray at Queen's Club in London.
Former world No.1 Murray was returning from an almost year-long lay-off due to a hip injury and looked to be in good touch after taking the first set.
Kyrgios was serving to stay in the match in the second against his close friend but bossed the tiebreak and then took the decider after the Scot double-faulted to win 2-6 7-6 (7-4) 7-5.
World No.21 Kyrgios said the troublesome elbow which saw him withdraw from last month's French Open was fine but admitted to feeling some pain in his hip against Murray.
"My elbow feels good, which is always a positive these days," he said.
"But 2-2 in the first set, I split-stepped and my hip kind of pinched a little bit. I was dealing with a little bit of pain for the whole match, as ridiculous as that sounds because the guy (Murray) was out with a hip injury."
It was Kyrgios' first victory over the two-time Wimbledon champion at his sixth attempt and also his first singles victory in west London.
He sent down 18 aces and was broken four times from 11 attempts, winning three from 11 on Murray's serve in his second consecutive match against former Wimbledon champions and top-ranked players.
Kyrgios lost to world No.1 Roger Federer in a tight semi-final at the Stuttgart Open last week.
"If I'm feeling good physically and if I believe in myself there is no reason why I can't go into Wimbledon as one of the serious threats," he said.
"I played well against Roger last week. Up 3-1 in the tiebreak serving. I wouldn't say we played unbelievable today, I played OK.
"I feel like I'm in good form on the grass. My timing, my hands are all good. I've just got to keep staying healthy, hopefully, and I'll be fine."
His next opponent is Brit Kyle Edmund. The Australian Open semi-finalist beat Ryan Harrison of the US 7-6 (7-4) 6-4.
"Kyle's been playing great," Kyrgios said. "I played juniors with him - I always knew he was going to be pretty good."
Earlier, 12-time major champion Novak Djokovic bounced back from his own French Open disappointment with a straight-sets demolition of Queenslander John Millman.
Djokovic, who lost to Italian giant-killer Marco Cecchinato in the quarter-finals at Roland Garros earlier this month, was rampant in a 6-2 6-1 win.
He will next face Grigor Dimitrov, who survived a tough first-round workout against Bosnia's Damir Dzumhur.
Milos Raonic also progressed but later withdrew due to a shoulder injury.