The Potters are currently sitting in 12th in the Premier League table - five points above the drop zone - in Hughes' first season in charge at the Britannia.
Goals have been hard to come by, with just 19 from their opening 20 top-flight games, and the Potters are being linked to West Brom striker Shane Long, who has just six months left on his contract at the Hawthorns.
While Coates is not ruling out a move in the market - he insists it must be the 'right deal'.
He told The Sentinel: "We are looking to see if we can bring someone in who's going to help us.
"But it is a tough market out there and it will not be easy.
"We are doing OK this season, but that doesn't mean we wouldn't strengthen the team if the right deal came along.
"Despite the difficult market out there, we are working hard on these things behind the scenes."