West Ham United assistant manager Nikola Jurcevic has conceded that the Hammers were mediocre in their 2-1 Europa League defeat to NK Domzale.
The London club started the game as favourites against the Slovenian side, but they never got going in the first leg of the third round qualifier.
The second leg of the tie will take place at Olympic Stadium next Thursday.
"First I want to say well done to Domzale because they won today and they were really good," said Jurcevic, who was in charge of the team on the day due to Slaven Bilic's two-game UEFA ban.
"Our performance was not so good, and maybe I can say it was average in the first half and it was 1-1. We were not satisfied with this result and in the second half was played bad and Domzale was the better team and won 2-1.
"OK, we were maybe not in our top form because it was our first official game and we were without some very important players and only had young players on the bench, but this is not an excuse, I must say.
"Domzale was better and I hope and I am sure we will be better next week. It will be very difficult but I'm optimistic and I hope it will be a different game in the Olympic Stadium. It's a special game because it's the first game at the Olympic Stadium with about 54,000 spectators.
"We must be better, we must win this game in our stadium because we also have big ambitions in Europe, but it will be very tough because Domzale showed they are a good team. We must improve next week, with more players back in the squad, and I hope we can win the first game at the Olympic Stadium."