Garry Monk was left a frustrated manager in the 2-1 defeat at Swansea after watching Wednesday fail to take their first-half chances.
The Owls boss said: “That was hugely disappointing today, We gave a performance in the first half when we should have been out of sight.”
Monk compared the display to the home game with West Brom in midweek, being the better team in the first half but failing to turn that into goals.
Reflecting on the Swansea game, he said: “We were so far on top in the first half and should have killed them off.
“The key today is we should have been giving them a big hill to climb in the second half. The stability would have been with us, they would have had to chase the game and we hopefully could have picked them off.”
The Owls boss added: “We had so many good opportunities in the first half but didn’t kill them off.
“Then, in the second half, a couple of moments of poor decision-making and rash moments and we find ourselves two goals behind.
“It’s been a bit of a common theme this season, where we have been on top but not been ruthless enough and then been undone by moments of madnesss and poor decision-making.”