Callum Johnson stopped by Artur Beterbiev as Daniel Roman beats Gavin McDonnell
British light-heavyweight Callum Johnson and super-bantamweight Gavin McDonnell suffered stoppage defeats in world title shots in Chicago.
Johnson, 33, was sent to the canvas by IBF world light-heavyweight champion Artur Beterbiev in round one but floored the Russian in the second.
But Johnson could not beat the count after a hard right hand in the fourth.
McDonnell, 32, was stopped after a 10th-round flurry by WBA world super-bantamweight champion Daniel Roman.
Doncaster's McDonnell had struggled in the early stages at the Wintrust Arena against the confident American, who closed space smartly to land the more eye-catching and venomous work.
Roman seemed confident to step in and take what McDonnell could offer in order to land at close quarters himself, including a solid left hook in the seventh.
McDonnell - sporting a bloodied nose - was warned he was trailing by trainer Dave Coldwell but his trademark workrate briefly saw him look more threatening for the two rounds before the stoppage.
When it came, Roman drove a right hand home, forcing McDonnell's knees to buckle and the champion followed with two crisp uppercuts in a flurry which overwhelmed the challenger.
While McDonnell rose to his feet, the referee waved the bout off, sealing the Briton's second defeat in a world-title contest after he was also bettered by Mexico's Rey Vargas in February of last year.
'It wasn't meant to be'
While McDonnell's bout threatened to go the distance, Johnson's never looked like it would reach halfway against a man who has now knocked out all 13 or his professional opponents.
Beterbiev's destructive reputation saw him installed as a heavy favourite against the British and Commonwealth champion, who had 17 wins from 17 before the bout but admitted he would need to "shock the world".
Both men were prepared to let their hands go early on, increasing the likelihood of an early finish. When Johnson briefly turned his back after tangling with the ropes late in round one, Beterbiev showed no mercy, landing a right hand to score a knockdown.
But Johnson gathered himself and found repeated joy with the left hook, clubbing the shot home to send Beterbiev down for the first time in his career in the second.
Boston-born Johnson may regret not swarming the champion in the immediate aftermath but perhaps conscious of the power which could come back his way if he over-committed, he remained poised.
And Beterbiev found a clean right to the temple two rounds later when the pair were again trading at close quarters, ending Johnson's dream of claiming a world title in memory of his father, who died in February 2016.
"It wasn't meant to be tonight," tweeted Johnson shortly after defeat. "Respect to my opponent but I know I can perform so much better than that and I'll be back better than ever. My time will come and I will lift a world title, 2018 is just the start of my career."