Briton Max Burgin stunned Olympic 800 metres champion Emmanuel Wanyonyi in the Rabat Diamond League meeting on Sunday while Kenny Bednarek eased to a supremely comfortable 200m win over Letsile Tebogo.
Burgin, 24, who was earmarked as a future world or Olympic medallist when he broke through the youth ranks before injuries hampered his progress, was simply too strong for Wanyonyi, the man who last year came close to breaking David Rudisha's 14-year-old world record.
The Briton's win in 1min 42.98sec, over half a second faster than Wanyonyi's 1:43.56, suggests he can aim for something special at the main event of the season, the new World Athletics Ultimate Championships in Budapest in September.
Wanyonyi said he realised he is the man to shoot at now: "I expected a race like this where someone would push me to my maximum. The race was so good, my fastest of the season. At the same time, it was very tough."
Bednarek blew away the men's 200m field to win in 19.69sec, a meeting record, as reigning Olympic champion Tebogo lumbered out of his blocks before the Botswanan found his running to break 20 seconds for the first time this season.
"Obviously, there are the Ultimate Championships. You are going to see fast times and good competitions out there. I like competing so I can't wait for another year," said American Bednarek.
The men's 3 000m steeplechase, the final event of the evening, was fittingly won by Morocco's two-time Olympic champion Soufiane El Bakkali who clocked a world-leading time for the year of 7:57.25.
Geordie Beamish, the New Zealander who created a huge shock by pipping El Bakkali to gold at last year's world championships in Tokyo, finished a distant 13th.
American Yared Nuguse dug deep to hold off fast-finishing world champion Isaac Nader of Portugal in 3:30.35 in a high-quality men's 1500 metres.
In the women's equivalent, Ethiopia's Freweyni Hailu unleashed a decisive final lap to win the sixth Diamond League race of her career in 3:58.25.
In the men's 400 metres, Jacory Patterson set a meeting record of 44.11sec in front of Britain's Olympic silver medallist from Paris, Matt Hudson-Smith, who clocked 44.25 in his season-opening race.
Quincy Hall, the man who beat Hudson-Smith to that 2024 Olympic title but who was beset by hamstring injuries last year, showed he still has a long way to go in his recovery as he trailed in last.
Tina Clayton powered to victory in the women's 100m, leading home a Jamaican 1-2-3 with a time of 10.85sec.
Audrey Werro, the Swiss athlete who made such an impressive breakthrough last year, was an impressive winner of the women's 800m in 1min 56.56sec, leaving the reigning world champion Lilian Odira of Kenya in third.
Tobi Amusan of Nigeria blasted to victory in the women's 100m hurdles and Ukrainian world record holder Yaroslava Mahuchikh took the women's high jump after clearing 1.97m.
Sri Lankan javelin specialist Rumesh Tharanga Pathirage is the top-ranked thrower of the year but the 23-year-old had to bow to two-time world champion Anderson Peters of Grenada. Pathirage threw 85.97 metres to Peters' winning effort of 86.08m.