Brook, 30, moves up almost a stone in weight to tackle the current 160 pound king and is already a massive underdog with the bookmakers to pull off a shock on September 10 in London.
UK rival Amir Khan recently did similar when going up eight pounds to battle Canelo Alvarez for the WBC middleweight crown at a catchweight of 155 and was duly knocked out badly in seven rounds.
Asked whether he believes the GGG v Brook fight could go the same way when taking in the Silverstone Grand Prix recently, Joshua told Sky Sports F1: “Anything below heavyweight and weight plays a big part – a massive part. It’s very possible, but I hope Kell Brook does well.
“If it would have been Gennady Golovkin v Eubank, then they are the same weight and it makes sense, but all credit to Kell Brook for taking the fight with no hesitation.”
Joshua is hopeful of returning to action himself around November or December once the current Olympic gold medallist takes in the action from the Rio 2016 games this summer.
Training should begin in September for what will be a second defense for Joshua as a shortlist of opponents, topped by Canadian Bermane Stiverne and New Zealander Joseph Parker, is considered by promoter Eddie Hearn.