Callum Smith
Callum Smith will be confident of following up his unanimous decision victory over Erik Skoglund Alex Livesey/Getty Images

After a pleasingly injury-free run in both the eight-man cruiserweight and super-middleweight divisions, the logistical difficulties involved in running a tournament such as the inaugural World Boxing Super Series (WBSS) have certainly been laid bare over the past few days.

Following a dislocated shoulder suffered by George Groves at the tail end of a comfortable points victory over compatriot Chris Eubank Jr on Saturday night (17 February) that could call his participation in the June final into question, rumours that Juergen Braehmer has withdrawn from this weekend's last-four clash with Liverpool's second-seeded Callum Smith due to illness has now been confirmed.

"I have been battling a feverish infection since Sunday," said the veteran former two-time light-heavyweight world champion on Tuesday. "Unfortunately, a fight in this state is out of the question.

"It is not possible for me to go into the ring like this and I would like to apologise to my fans. I was well prepared and looking forward to fighting Callum."

The show will continue without Braehmer, who dropped back down to super-middleweight for the first time in a decade for his comprehensive quarter-final defeat of Robert Brant, with promoter and competition chief Kalle Sauerland corroborating speculation that Nieky Holzken - who had apparently been on standby as a reserve - will step into the breach at the Arena Nurnberger Versicherung.

Who is Nieky Holzken?

'The Natural', who hails from the city of Helmond in the southern Netherlands, was actually due to fight on the undercard in Nuremberg against former WBA interim middleweight champion Dmitry Chudinov, who presumably was not considered as a potential replacement having lost to 45-year-old Lolenga Mock on his last appearance in Copenhagen in January.

Eyebrows will likely be raised that Holzken has only contested 13 fights - all victories with 10 knockouts - and 54 rounds by age 34, though that is because he also competes in kickboxing and Muay Thai.

The undefeated Dutchman is certainly well respected in both sports, having been a seven-time world champion in one and and a two-time European title-holder in the other in addition to winning the K-1 MAX Scandinavia tournament in 2006.

Holzken appears to have tended to switch between the disciplines in recent years rather than commit to any one full-time, with his professional boxing debut - a second-round KO in a four-rounder against Anatolij Baron in 2013 - coming 11 years after the beginning of that storied kickboxing career.

He has also stopped Ata Dogan, Philipp Kolodziej, Gary Abajyan, Ismael Altintas, Ruslan Shchelev, Mikheil Khutsishvili, Yesilat Berkta and Cagri Ermis since then as well as outpointing Ahmed El Ghoulbzouri, Farouk Daku and Matingu Kindele.

His last contest came only on 3 February against ex-Ukrainian Olympian Viktor Polyakov, whom he beat in impressive fashion in the second round at Hemmers Gym to retain his Benelux super-middleweight title.

12 of those first 13 boxing encounters have come in Holzken's native Netherlands, 10 in Helmond, one in Eindhoven and another in Amsterdam. His victory over Berkta in November 2015 was staged in Meppen, Germany.

This is an obvious step up in class against 27-year-old British and WBC Silver champion Smith, trained by Joe Gallagher and the younger sibling of fellow boxers Paul, Stephen and Liam, who is unbeaten in his 23 pro encounters to date (17 KOs).

'Mundo' has also yet to fight at world level and beat Erik Skoglund via a unanimous decision in front of a hometown crowd at the Echo Arena last September.

What have they said about the fight?

Holzken: "I've been waiting for this chance to come. I signed up as a substitute fighter so I'm in great shape and prepared for Saturday.

"I've watched Callum fight many times. I study everyone in my weight division. He's a good, solid fighter. We're both big body punchers. It will make for an excellent fight. Callum, you better be ready, because I am, and I'm coming to beat you."

Smith: "I gave an interview last week and said it's great there have been no drop-outs. Looks like I spoke too soon.

"We got the call as we were boarding the plane. I am committed to fighting on Saturday and will fight whoever the World Boxing Super Series puts in front of me."

Juergen Braehmer
Juergen Braehmer beat Robert Brant in October to qualify for the WBSS super-middleweight semi-finals Martin Rose/Bongarts/Getty Images
Twitter/@niekyholzken