OF all the boxers I’ve ever seen spar, none have been tougher than Lithuanian light-heavyweight Sergey Rozvadovskij.
Hands up, chin down, he’d use large forearms to construct an impenetrable wall around his face and then use an unbreakable will to march down whoever was unfortunate enough to be in his way. Unflustered, he did this round after round, never once complaining, never asking for a break or a day off, and if told there was to be a 30-second rest between rounds, as opposed to the customary minute, he offered merely a shrug.
Sergey Rozvadovskij got on with it. He treated sparring as his day job and soaking up the punches of better-known boxers a daily requirement of said job. Even Gennady Golovkin couldn’t put a dent in him.