The FA has declined to comment on whether Saido Berahino served a eight-week suspension before he joined Stoke.
The Daily Mail and Guardian have reported Berahino tested positive for a recreational drug during his time at West Brom and served an eight-week suspension.
Both Stoke and West Brom have confirmed that Berahino, who signed for Stoke last month after completing the ban, had been in hot water with the FA.
Hughes, speaking at a press conference covered by the club’s website, www.stokecityfc.com, said: “We are aware of it clearly – there was an FA disciplinary matter and Saido had an eight-week suspension, I believe. We were aware of that before we signed him.
In terms of more detail you would probably need to refer back to his former club. We aren’t in a position to give any more details as we don’t have them.
“He had issues at his previous club for 18 months, which this is obviously a part of.
“As with all players we did our research on him before we signed him, but that didn’t change our thinking at all.
“We are pleased with what he is producing and he is looking forward to the game tomorrow.”
Tony Pulis, the West Brom manager, also confirmed the ban on Friday. “Saido served a ban while he was here but I won’t comment why. He didn’t play for me because he wasn’t fit enough,” he said.