John Fleck's double was enough for Chris Wilder's Sheffield United to beat Aston Villa for the first time in the top flight since 1991.
Villa have only only won one of their past seven games, with only goal difference keeping them outside the bottom three.
Jack Grealish missed a late penalty to have Villa's deficit as his spot-kick rattled Dean Henderson's crossbar.
Dean Smith spoke to the AVFTV after leaving Sheffield empty-handed.
"We're going through a frustrating period at the moment, but I believe in the quality of the players.
"We didn’t manage the ball well enough, and we should do with the players that we have. It was a game of few chances and it was littered with fouls. They deserved to win."
Sheffield United boast the third-best defensive record in the league having conceded just 16 goals in their first 17 games this term. Though Smith rued his side's lack of conviction in front of goal as Villa drew blank for the fourth time this campaign.
"I thought we made it difficult for them, but they took their chances and we didn’t take ours."
Brazilian forward Wesley has not found the net in his last nine starts. He was replaced by Jonathan Kodjia after the hour mark.
Smith said: "I thought he was a lot better today. He had a couple of chances but he took a whack on his lower back, so it was time to give Kodjia an opportunity."
The Villa head coach revealed that Conor Hourihane will be in contention to play his part in a Carabao Cup quarterfinal against Liverpool, after missing the trip to Bramall Lane through injury.