David Moyes says West Ham "didn't show enough quality" as they sank to a 2-1 Europa League semi-final defeat to Eintracht Frankfurt.
It was West Ham's first European semi-final for nearly 50 years, but it ended in disappointment at the London Stadium, with them now needing to go to Germany and win in the second leg.
Frankfurt took the lead in the first minute courtesy of a Ansgar Knauff header but were quickly back level through Michail Antonio.
An expectant home crowd then expected the Hammers to push on and win the game, but it was the visitors who forged ahead again with Daichi Kamada scoring.
Despite creating plenty of chances - and hitting the woodwork three times - West Ham were unable to make any further inroads.
"We've got a lot to do," a frustrated West Ham boss David Moyes admitted. "We've got to show a lot more quality than we did tonight.
"We didn't show enough quality, especially in the final third when we had moments to do so and a couple of times we turned off, obviously for the goals.
"So, a lot of those things will need to brighten up and be better."
He added: "Ultimately a disappointing result for us, but we've still got another game to play and we've given ourselves a chance still and hopefully we'll play better in the second leg."
Frankfurt arrived at the London Stadium on a high after knocking out Barcelona in the previous round, and Moyes admitted he was impressed with the Bundesliga outfit.
"I think Frankfurt made it difficult which, to be fair, they're renowned for, they're very good at it," added Moyes.
"We didn't start the first half so well, nor the second half. They scored the goals in those periods.
"We started and they scored within a minute and it was a terrible start for us, but I felt after that we grew into the game, we got a goal.
"If you said to me who was more likely then I felt we were at that period of the game, but we weren't able to take it."