The last time Anthony Joshua fought a replacement for his original opponent, Andy Ruiz Jr. dropped the then-unbeaten heavyweight champion four times, upset him by seventh-round technical knockout, took Joshua’s four titles and forever altered the British superstar’s career.

Four years later, Joshua knows better than to overlook Robert Helenius, who replaced Dillian Whyte due to what were called “adverse analytical findings” in Whyte’s performance-enhancing drug tests in Matchroom Boxing’s press release Saturday to announce Whyte’s removal from his rematch with Joshua. “The Nordic Nightmare” took their fight on less than one week’s notice, but numerous sparring sessions with the huge Helenius have taught Joshua (25-3, 22 KOs) that his 6-foot-6, 250-pound opponent will be dangerous Saturday night at O2 Arena in London.

“It’d be silly to underestimate Helenius, silly to underestimate anyone,” Joshua said during a press conference Wednesday in London. “So, I’ve gotta take him deadly serious. And credit to him as well. He’s coming to roll the dice. He wants to win. As you mentioned, other heavyweights, [with] certain people obviously finance is the big issue, risk versus reward. But in reality, that’s not all there is to this for him. He wants to win, so he’s here. So, good luck to him.

“And shout out to everyone in Finland as well. I’ve been there before. And we’re looking to combine UK, Finland and the rest of the world to bring some good entertainment from the top right to the bottom. The undercard is phenomenal. So, yeah, don’t miss a fight. Do not miss a fight because this card is unbelievable.”

Though this is the third time in Joshua’s 10-year professional career that he has agreed to face a substitute, Helenius (32-4, 21 KOs) replaced Whyte (29-3, 19 KOs) on shorter notice than Carlos Takam stepped in for Bulgaria’s Kubrat Pulev in October 2017 and Ruiz replaced Brooklyn’s Jarrell Miller four years ago. Joshua was afforded approximately five weeks to prepare for Ruiz and about two weeks to get ready for Cameroon’s Takam, whom Joshua stopped in the 10th round at Principality Stadium in Cardiff, Wales.

“Late replacements aren’t ideal,” Joshua said. “But I’d say this is the third time it’s happened. We had it with Kubrat Pulev and Takam, Jarrell Miller and Ruiz. Now this situation, so this is what happens. A long career, we’re all presented [with] these types of obstacles, and I’ve just gotta get used to ‘em. So, yeah, this is just another rock in my shoe on towards the top of the mountain.”

Helenius, 39, will fight for the second time in only eight days when he encounters Joshua in a 12-round main event DAZN will stream worldwide.

The Swedish-born, Finland-based veteran defeated Finland’s Mika Mielonen (6-1, 6 KOs) by third-round TKO in their scheduled eight-rounder last Saturday night at Olavinlinna, a castle in Savonlinna, Finland. Helenius’ victory marked his return to the ring from a devastating first-round knockout loss to former WBC champ Deontay Wilder (43-2-1, 42 KOs) last October 15 at Barclays Center in Brooklyn.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.