Forward Fernando Forestieri blamed tiredness for the Owls’ below-par showing at struggling Charlton Athletic.
Carlos Carvalhal’s side go into the two-week international break having tasted their first defeat in nearly two months.
Charlton dominated for long spells and comprehensively secured their first victory since August.
Forestieri accepts there is plenty of room for improvement and is calling on Wednesday to learn lessons from their capital humbling.
“We are so sad because we had a good chance to win,” said Forestieri, who bagged a late consolation for the Owls. “I don’t know what happened to us in the first half. They won the second balls and were more aggressive.
“In the second half, we improved a little bit but it was too late at 3-0.
“We need to take the positives, learn from the mistakes we made and improve a lot of things.
“We need to focus 100% at the beginning when we start the match. We need to learn quickly because the Championship is a difficult league and anyone can beat anyone.”
The former Watford player claimed Wednesday’s goalless draw with Brighton and Hove Albion, the Championship’s surprise package this season, last week took its toll on the squad.
Five-goal Forestieri said: “We lost because we did a lot of running in midweek.
“We changed just one player (Gary Hooper) and everybody else played 90 minutes on Tuesday. We were tired and now we need to think about recovering well.
“It (the international break) is very good to us. You can play seven games in one month in the Championship so it is a lot of games for the players.
“We can now recover well and start more strong, focused and compact. We need to improve and listen to what Carlos says to us.”