Gomes came up against United and Wilder during the Blades' promotion campaign to the Premier League, and the current Marítimo boss has watched from afar as Wilder's men established themselves in the top-flight.
He told the Coaches' Voice: "Sheffield United played with three defenders but I have watched millions of games, and I have never seen anything like that.
"At times the wing-back had the ball and the centre-back was overlapping him, asking for the ball in the front of him.
"There was a fantastic dynamic with very strong team movements, and that is not easy to stop.
"They were very confident and had a great, great season. Really played like a team.
"You can study a lot of teams who play with three defenders but it is difficult to study the movements they did last season.
"There's a lot of intensity in their movements and in the capacity of their players, and they play like a team.
"All the players know where they should be in the end of the action, and their manager did a great job.
"In all my career, this was the biggest challenge I have had as a manager."