Cowan, who played with Hughes for New South Wales and against England in the 2013 Ashes series, is stunned that McClenaghan's safety equipment is not up to date.
Cowan has described the day he knew Hughes would not recover as the worst of his life.
After McClenaghan went down, he said: "Another victim to a ball through the grill of an old Masuri helmet. How they were ever deemed safe is beyond me."
Boult, who replaced McClenaghan at the crease, said: "It's tragic what has happened over the last wee while...it churns your stomach and is hard to talk about, but we've got to move on.
"Short pitched bowling is something I fear, but with the technology that goes into supposedly indestructible helmets, they've come a lot way.
"Every step is taken to make sure we're safe. Unfortunately one snuck through and got him good.
"Mitch was wearing an older helmet I believe, I think that's down to his personal preference. It's never nice seeing one of your teammates on the ground, it is a scary part of the game, but has been going on for years.
"With new helmets that supposedly can't happen. The visor gap between the grille and the lid is supposed to be smaller."
