David Haye is certainly an expert in making the big jump from cruiserweight to heavyweight.
Haye, who unified three of the cruiserweight world titles, moved up to heavyweight and eventually toppled the seven-foot Nikolai Valuev for the WBA world title.
Oleksandr Usyk is looking to make the same leap this Saturday night.
Last year, Usyk became the first cruiserweight to unify all four of the major sanctioning titles in his division, as he cleaned out the entire weight class with victories over just above every top name at the weight.
Usyk was scheduled to face unbeaten Tyrone Spong on Saturday night in Chicago. That fight is not likely, as news broke on Monday that Spong tested positive for a banned substance in random drug test administered by VADA. The replacement opponent has yet to be finalized.
Haye believes Usyk's attributes alone would beat most of the boxers at heavyweight, but he wonders how the boxer would do against very tall boxers like Deontay Wilder or Tyson Fury.
"I've always thought he has a great chance because he's so skilful. His defence is the most important thing as a cruiserweight moving up to heavyweight. You've got to be super tough or have a great defence, or punch extremely hard. Evander Holyfield was super tough - he was able to block, ride and parry punches. I punched extremely hard," Haye told Sky Sports.
"Usyk is different - he is not a one-punch specialist, he throws clusters of punches. He is a southpaw so is tricky to hit clean. He punches from different angles. This will be enough to beat 90 percent of heavyweights but whether he can do it against someone who is 6'6'' remains to be seen. It looks like he can.
"[The fact that he beat Joe Joyce in the amateurs] proves he can handle a big guy. It was only a three-round fight but Usyk was comfortable and the size didn't make a difference. That was as an amateur, and it was a while ago."