He knows he's punching harder and faster than ever – the big question is, how will it affect Joshua?
Publicly Joshua always appears composed, but whispers behind the scenes suggest that's not always the case in private. Will Parker's surgery late last year, which will be leveraged to the fullest by him and his team over the next few days, ruffle the Englishman?
Joshua and his team would have based their research on Parker's last half dozen fights, bouts in which the Kiwi-Samoan has stopped only two opponents.
In the others – points victories over Carlos Takam, Andy Ruiz Jr, Razvan Cojanu and Hughie Fury, Parker has swung from very impressive to fairly flat, despite the high stakes involved.
Some of his punches have been more like slaps than pistons, an offence which has left little impression on some of his opponents – most notably former sparring partner Cojanu and Fury, but both of them entered the ring to survive rather than attack.
Joshua, who has won all 20 of his professional fights inside the distance, will not be trying to merely survive. He will be eager to try to shock Parker with his power and aggression at the Principality Stadium on April 1 NZT, knowing that his opponent is fast but not necessarily in possession of one-punch knockout ability.
The Herald's revelations that Parker is not the same man who had to put his faith in the judges four times in the last couple of years might make Joshua and his team pause for thought a little.
Parker knows what he's going to get with Joshua – he worked out daily in his Las Vegas gym with replays of the Joshua v Wladimir Klitschko fight at Wembley running on a continual loop. But does Joshua know what he's going to get from Parker?
The surgery news won't make the bookies rush into change their odds or the favourite, which is, by a big margin, Joshua. But this fight might be closer than many people think.
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