Carlos Carvalhal says his side’s second half recovery was too far undermined by the opening period in which Wednesday were outplayed by Middlesbrough.
The Owls were then caught by a sucker punch minutes after equalising and Boro went on to score another to emerge 3-1 winners.
Carvalhal said: “If we are to win matches then we must play for the full 90 minutes, not half of the game.
“In the first half, I was not happy because we watched too much of the game instead of playing it.
“I was very happy with the way we played in the second half but the second goal really hurt us.
“We were moving forward because we wanted to win the game but we were caught on the break. At that point, I was really disappointed and it was frustrating because I thought we could win the points.
“But the story of this game is that the first half performance did not match that of the second and we were punished.”