Anthony Joshua volition combat Robert Helenius astatine London's O2 Arena connected Saturday arsenic the replacement for Dillian Whyte.
Joshua's heavyweight rematch with Whyte was cancelled astatine the play aft the second failed a voluntary cause test.
Finland's Helenius, who has 32 wins and 4 losses, steps successful astatine little than a week's notice.
"This wasn't successful the script," Joshua said of his caller opponent. "I americium laser focused connected the win."
Helenius' past large combat was a first-round knockout decision by Deontay Wilder successful October.
"I americium a existent Viking that is consenting to look immoderate situation astatine a moment's notice," the 39-year-old said.
"This is not an accidental I was going to fto gaffe away. I program to marque the astir of it."
Helenius, who has ne'er challenged for a satellite title, lone fought connected Saturday, securing a third-round TKO triumph implicit Mika Mielonen successful Finland.
As good arsenic Wilder, the 6ft 6in Helenius has losses to Gerald Washington, Whyte and Johann Duhaupas.
A triumph would acceptable Joshua up for his long-awaited combat with erstwhile WBC champion Deontay Wilder, which could hap aboriginal adjacent year.
Joshua is undefeated astatine the O2 Arena successful London and won astatine the venue successful April erstwhile helium outpointed Jermaine Franklin.
Joshua, 33, held talks with galore heavyweights already connected his undercard, including American heavyweight Washington, to regenerate Whyte, but promoter Eddie Hearn said galore opponents priced themselves retired of the running.
According to Hearn, Joshua reacted "calmly" to the quality of the cancellation of the combat aft the Voluntary Anti-Doping Association (Vada) informed promoters Matchroom and boxing authorities of Whyte's trial result.
"With a week to spell earlier 1 of the biggest fights of the twelvemonth I was shocked and dumfounded. AJ sent maine a connection which was unbelievably calm," said Hearn.
"AJ is hopeless to fight. He has looked unbelievable successful camp. I person ne'er seen him successful specified bully shape."
The combat betwixt Joshua and Whyte, a rematch of their 2015 bout, was announced successful July.
Joshua knocked retired Whyte successful the seventh circular of their heated British rubric combat 8 years ago, which besides took spot astatine the O2, arsenic helium avenged a nonaccomplishment to his rival connected the amateur circuit.