Leyton Orient boss Russell Slade admitted his side have made life very difficult for themselves after their 1-0 home defeat to Southend United.
The O's will have to win at Roots Hall in a fortnight to have any chance of going to Wembley in the Johnstone's Paint Trophy.
But Orient created enough chances to have secured a result in the first leg with David Mooney having a hat-trick of good chances to score against the excellent Southend keeper Paul Smith.
Slade said: "It's a really frustrating night for us. The conditions weren't great but that was the case for both sides. We created enough on the evening to get ourselves a couple of goals but unfortunately we've not. We trail now and it's made life very difficult for us.
"He [Smith] was well worked and made some good saves and kept them in the game. David Mooney had chances particularly in the second half.
"It was a great little move with Moses Odubajo doing well down the right and you'd have expected Mooney to put that in with the recent form he's been in but he hit the crossbar and it bounced straight back down just above the goalline. It didn't go our way but there's a lot to play for and it's still only half-time."