Liverpool manager Jurgen Klopp was bitterly disappointed after his side's 1-0 home defeat against Manchester United.
The Reds desperately needed all three points to keep their Top Four hopes alive.
Instead, they are now eight points from fourth-placed Tottenham Hotspur with a number of tricky away games coming up in the next few weeks.
"I didn't see too many chances for Manchester United and we didn't take ours," Klopp told BBC Sport.
"Of course it is frustrating. We lost a game that we should not have lost.
"The goal was to defend and we didn't do it. That is our responsibility. We have to defend set pieces better.
"We did really well creating the chances, but there were a lot of situation where we could have created more chances and didn't.
"There were a lot of things but we lost in a derby against Manchester United so I can't be very positive at this moment so soon after the game."