The withdrawal of the World Boxing Organisation middle-weight champion, Bert Schenk, with a ruptured Achilles tendon threw Matthews' plans into disarray after he had trained for two months for his title chance.
However, his promoter, Frank Warren, has been working to find "Method Man" Matthews an opponent since Schenk pulled out last week and even had plans in place for him to fight on a hastily-arranged show at York Hall, Bethnal Green, to fill the Sky television date and ensure that the Hackney fighter's preparations did not go to waste.
Matthews, beaten once in 22 fights, said: "I'm glad the problem is sorted out. I just want to fight and prove that I am the best middleweight in the world. I've been preparing for Schenk, but he just keeps pulling the sick note on me."
The Swedish-born Krajnc, 26, holds the German international title and has won all his 21 bouts, 14 inside the distance.
Richard Hatton will meet the former British light-welterweight champion Mark Winters in a defence of his WBO Intercontinental title at the Everton Park Sports Centre, Liverpool, on 11 December.
Hatton, from Manchester, was due to top the bill at York Hall last week but was ruled out by a bout of flu. "I'm looking forward to facing Winters. He's been in with some top names, such as British champion Jason Rowland," said Hatton.
His fellow Mancunian, Michael Gomez, will share top-billing with Hatton in Liverpool when he also defends his WBO Intercontinental title.
Gomez has been ordered to defend his British super-featherweight title against Dean Pithie of Coventry by the end of February next year.