Oleksandr Usyk emerged a serious danger to world heavyweight titleholders Anthony Joshua and Deontay Wilder on Saturday.
The Ukrainian unanimously outpointed Murat Gassiev to become undisputed world cruiserweight champion after delivering a boxing masterclass that set alarm bells ringing for the elite heavyweights.
If Usyk (15-0, 11 KOs) was a wolf in sheep's clothing stalking from the outside before Saturday, he is now a real threat for the heavyweight champions and contenders.
Moments after defeating Russian big-hitter Gassiev for the WBC, WBA, IBF and WBO world cruiserweight titles in the World Boxing Super Series (WBSS) final, television pundits and social media were calling for Usyk to step up a division.
Some were even calling for him to fight WBA-IBF-WBO world heavyweight champion Joshua next year. Usyk, 31, won the heavyweight gold medal at the 2012 Olympics, when Joshua won gold at super-heavyweight, and they have both been irresistible forces in the professional ranks since.
"I honestly think he would give Anthony Joshua a run for his money," said former world featherweight champion Naseem Hamed on ITV Box Office.
"I would like to see him fight AJ. He can work for 12 rounds. He would give Anthony serious problems. I think he can do the same thing [deliver a performance like the one against Gassiev] even against Wilder."
Joshua's promoter already has Wembley Stadium booked for April 13 next year and is hoping American Wilder, the WBC titleholder, will accept his $15million offer for that date.
But rather than Joshua, Usyk is more interested in another Briton and called on Tony Bellew (30-2-1, 20 KOs), 35, to face him next after the scintillating performance against Gassiev.
"At this moment I heard that Tony Bellew is looking for winner of the World Boxing Super Series and I hope he will see me talking," WBC-WBA-IBF-WBO world cruiserweight champion Usyk said.
"Tony Bellew, are you ready? If he doesn't want to go down [to cruiserweight] I will go up [to heavyweight] for him. I will take extra spaghetti for dinner for him."
Usyk I was BORN READY!! Let's get this done!! 👊— Tony Bellew (@TonyBellew) 21 July 2018
I'M ALSO READY! 🔥 https://t.co/hUcQeEdx9F— Alexander Usyk (@usykaa) 22 July 2018
Bellew replied via Twitter: "Usyk I was BORN READY!! Let's get this done!!"
Usyk won't mind travelling to the UK to face Bellew as his win over Gassiev was his sixth consecutive world title fight outside of Ukraine, five of which have been in the home nation of his opponent.
Bellew is a former WBC world cruiserweight champion who has stopped rival British heavyweight David Haye, another former world cruiserweight champion, twice in his last two fights.
That would be a good fight for Usyk to acclimatise to the heavyweight division -- and a real challenge for Bellew.
As Usyk showed against Gassiev, his sublime skills and relentless energy could cause serious problems for Bellew, Joshua or Wilder if he can avoid the bigger men's power punches.
Not since Evander Holyfield 30 years ago has there been a cruiserweight with so much potential at heavyweight as the the father-of-three from Crimea, a region annexed by Russia in 2014 a year after Usyk turned professional.
He will have to contend with a size disadvantage when he steps up as Joshua outweighs him by more than two stones at the moment.
But former cruiserweights -- even middleweights -- have succeeded at heavyweight. After becoming undisputed world cruiserweight champion in 1988, Holyfield stepped up to heavyweight and was 208 pounds (Usyk weighed in at 198¼ pounds for Gassiev) when he knocked out James 'Buster' Douglas to become undisputed world heavyweight champion in 1990.
American Holyfield overcame sizeable weight disadvantages to beat the likes of Douglas, George Foreman, Larry Holmes, Riddick Bowe and Mike Tyson in four reigns as world heavyweight champion.
Haye, a former world cruiserweight champion, won the WBA world heavyweight title by using speed and boxing IQ to beat Russian Nicolay Valuev, who was seven stones heavier, in 2009.
Before him, former middleweight champion Roy Jones Jr outpointed fellow American John Ruiz for the same world heavyweight title belt in 2003 despite a 33-pound (2.3 stones) weight disadvantage.
After clearing up at cruiserweight with three dazzling displays in the WBSS, an eight-man tournament that began last September, bigger fights await Usyk at heavyweight.
Gassiev was the last remaining threat to Usyk at cruiserweight and went into the fight as WBA-IBF champion. But the Ukrainian won by scores of 120-108, 119-109 and 119-109 after controlling much of the bout behind his southpaw right jab, landing 252 punches to Gassiev's 91, according to CompuBox.
But there is so much more to Usyk's game than the jab, which his countryman Wladimir Klitschko relied so heavily on in his nine-and-a-half reign as world heavyweight champion until November 2015.
Usyk uses his technique, skills and stamina to break down his opponents and nullify them, rather than bludgeon them into the canvas.
Gassiev (26-1, 19 KOs), 24, who was making his third title defence, landed clean right hands in the fourth and seventh rounds, but Usyk absorbed them without showing any concern.
Gassiev was out of ideas by the eighth round when it became quite one-sided.
Usyk turned on the style, unloading more punches while always sustaining his piston-like jab. He finished the ninth round with a stunning combination and a precise left uppercut and, when Gassiev threatened, the Ukrainian danced away on twinkle toes.
Usyk's friend and fellow Ukrainian Vasyl Lomachenko, regarded as the world's best pound-for-pound boxer, admired the performance from ringside. Lomachenko's father Anatoly was in Usyk's corner and the undisputed world cruiserweight champion looked like a bigger version of lightweight Vasyl Lomachenko at times.
No one has boxing ability or hand speed at cruiserweight or heavyweight like Usyk and the clamour to see him fight the best at heavyweight has already started.