Virgil van Dijk rued Liverpool's efforts at both ends of the pitch after their 2-1 defeat against Manchester United at Old Trafford.
The Reds found themselves two goals down at the break having seen a difficult first-half performance twice punished by striker Marcus Rashford.
Jürgen Klopp's side responded in the second period, pulling one back by forcing Eric Bailly to put through his own net just past the hour mark.
But they were unable to find another goal as the Red Devils successfully defended their lead from a deep position across the remainder of the match, much to Van Dijk's dismay.
Asked for his feelings at full-time, the Dutchman told Sport 1: "Frustrated.
"Obviously to concede two almost identical goals was frustrating and it was difficult to break them down today because they sat back waiting for the counter-attack.
"Unfortunately, we couldn't break them down.
"First of all, we don't need to concede the two goals in the first half; for the rest, it was difficult to break them down, they sit and hope for the best on the break.
"We needed to try to break them down but it wasn't good enough."
Liverpool's bid to leapfrog their rivals into second place in the Premier League sustained a blow as they lost out in Manchester, with United taking a five-point lead as a result of their win.
But Van Dijk doesn't believe the setback will prove fatal to the Reds' top-four hopes, at least.
He added: "There are plenty of games left. Today was a big one but we need to move on and look ahead - it starts next week."