The 30-year-old former Sunderland striker was poised to join the Championship outfit from Chinese side Shanghai SIPG, but Stam on Wednesday revealed the deal fell through because Gyan failed a medical.
“Yes. He wasn’t in very good shape. When he joined us they did a very good medical on him which was very important because he’s been injured in the past. He hasn’t been playing a lot of games,” said Stam.
“You need to be sure, if you bring a player in, that he’s fit and not that you need to work him for six to eight weeks to get him in shape. And maybe there’s a risk of him getting injured during that period so he’s out for a longer time.
“And then he needs to go to Ghana in January and we lose him for two months. So it’s a big risk.
“He wasn’t in good shape, that was the case. Of course the player says he was in good shape because he wants to play, but he wasn’t. Our medical people are not going to be lying about that.
“That’s why we made the decision not to sign him.”
Gyan eventually joined United Arab Emirates club Al Ahli on loan after Reading pulled out of a move for the striker.
Dutch boss Stam also claimed Gyan, who signed for £13million for Sunderland in 2010, was not a too costly proposition.
“To be honest he wasn’t that expensive and you have to think why can he leave his club? Is there a reason he can leave that club if he’s that fit?
“So you have to think about that as well. But we’re always looking for quality strikers,” added Stam.
“He did well here in the UK, he did well in Saudi Arabia, in China and with the national team. If you see him play you can see he’s a quality striker.
“But we have to be sure because we don’t have much money to spend on players or wages.
“If we’re going to be spending money then we need to be sure it’s on a player who is fit and ready to produce for us.”