Darren Young admits one mistake cost his Fifers against Montrose in their second round Betfred Cup tie
A second half Danny Cavanagh was all that separated the sides in a game short on clear cut chances.
But Young reckons his side should have given themselves the chance of a second point in a row had it not been for some slack marking for the Mo goal.
He said: "Defensively I thought we looked pretty solid apart from once when we didn't match the runner and got punished.
"On Saturday that never happened, we matched our runners and got the blocks in.
"Tonight the one mistake cost us.
"But near the end we stuck Anton Dowds and Kevin Smith on and they did very well.
"I don't know why it took us to last 15 minutes to creating chances and getting balls into the box though.
"We need to learn from it."
East Fife made an encouraging start against newly promoted Mo and pressed them back deep into their own half.
Pat Slattery fired an effort over the bar before Craig Thomson pulled a save out of Jordan Millar.
The rest of the half, though, really lacked quality, and by the time ref Kevin Graham mercifully brought it to an end neither side had really troubled the other.
The second 45 started in the same manner as the first with too many misplaced passes and a general lack of urgency from either side.
Mo had started marginally the better of the two and snatched the lead out of the blue when Danny Cavanagh raced into the box to meet a cross and rifled past Brett Long from eight yards.
The goal opened the game right up and forced Fife boss Young into a double substitution as he chased the game.
Anton Dowds made his senior debut for the Methil side as was introduced along with Kevin Smith.
But it was the home side who went closest to scoring the game's second with Cavanagh's acrobatic effort dropping wide of the post.
At the other end Thomson again tried his luck with an effort Millar smothered with ease.
Ross Campbell should have wrapped up the win with 10 minutes to go when he raced in on goal and only had Long to beat.
But the forward managed to get the ball stuck beneath his feet and the Fife goalie managed to paw the ball into his possession.
East Fife should have snatched a draw in the closing seconds when Dowds met a Thomson cross six yards out only to nod over the bar.
Montrose - Millar, Ferguson (Watson 61), Steeves, Bolochoweckyj, Dillon, I Campbell, Masson, Fotheringham (Allan 74), Skelly (Johnston 46) Cavanagh, R Campbell.
Subs - Fleming, MacFarlane.
East Fife - Long, Dunlop, Dunsmore (Kane 84), Watson, Meggatt, Davidson, Watt, Slattery (Smith 64), Thomson, Court (Dowds 64), McBride.
Subs - Couser, Bell, Smith.