Ex-Wales captain Rees was dismissed after connecting with Nick Easter's head at a second-half ruck in the European Challenge Cup clash.
"There's definitely no malice in it. It looks possibly like a clumsy situation," said Wilson.
Rees will face a disciplinary hearing to determine any punishment.
But Wilson hopes the player's record will be taken into consideration.
"Matthew is not that type of player. He's a very diligent professional with an extremely positive record behind him, which hopefully will go with him when it's discussed," said Wilson.
Blues lost Wales captain and flanker Sam Warburton to a virus before kick-off.
That forced a back-row reshuffle in which Ellis Jenkins moved to open-side, but he departed because of injury after 52 minutes.
Quins went on to secure a bonus-point win.
Cardiff Blues coach Danny Wilson says there was "no malice" in the apparent stamp that saw hooker Matthew Rees sent off in the loss to Harlequins.