Carlos Carvalhal said Sheffield Wednesday's match against Leeds United at Hillsborough swung on the first goal, as the visitors came out 2-0 winners in the Yorkshire derby.
Marcus Antonsson put Leeds in front in the second half and Chris Wood doubled the advantage late on to give Garry Monk's side a deserved win, but Wednesday were hugely disappointing.
The defeat capped off a tough week for Carvalhal and his side, coming off the back of the controversy surrounding Fernando Forestieri and his no-show at Norwich City last week, as well as defeat to Burton Albion in midweek.
Two defeats on the spin has now taken the shine off an impressive four point haul against Aston Villa and Norwich and made for a start to the campaign, more reminiscent to last season which took a while to get going.
"This is a disappointing result after a good start to the season with the performances against Aston Villa and Norwich," said Carvalhal.
"The game was very physical today and although we ran a lot, we didn't necessarily run properly. The balance of the squad at the minute is not 100%, some players are fitter than others after pre-season, but this cannot be an excuse.
"We had strong momentum going into the Burton game (in midweek) and we were playing good football, but I think that loss made our confidence and our energy suffer.
"We wanted the same performance today as we had against Villa and Norwich but it wasn't the case.
"It was important to score the first goal today and although we made a number of chances in the first half we didn't do that. We responded well after conceding and created three or four chances, but fell victim to the counter-attack from Leeds."