Carlisle United's Paul Simpson on Cambridge United defeat

Simpson said the Blues only have themselves to blame for the manner of their 1-0 setback at the Abbey Stadium.

Carlisle had Jack Armer and Alfie McCalmont sent off in the closing stages but Simpson had little objection to either red card.

Instead he focused on Carlisle’s shortcomings in the match in general against a side who were winless in eight league games before kick-off.

“It was an opportunity missed,” he said.

“It’s not as if we’ve come to a team who are absolutely flying and picking up wins left, right and centre.

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“It was a team who were really low on confidence and when you have that opportunity you have to go and get right into their faces and be ruthless.

Simpson issues instructions during the defeat (Image: Richard Parkes)

“Instead we’ve been whatever the opposite of ruthless is.”

George Thomas’s 74th-minute header was the difference as Carlisle, after a decent start, faded badly as things went on.

It saw them drop into the League One relegation zone in 21st place.

“There’s nobody else to blame but ourselves. Let’s not look at blaming anybody else, it’s our own fault,” added Simpson.

“If you don’t do the basics well then you don’t get anything out of the game and unfortunately we haven’t done that.

“The biggest disappointment is that after a really good week of two good performances against Portsmouth and Burton we’ve been way off it this time in terms of football – we’ve turned over possession so many times and one of the times culminated in the goal we conceded, which gave them a lift and ourselves a mountain to climb.

Paul Simpson applauds United's fans after the defeat (Image: Richard Parkes)

“In terms of competing, we haven’t won our duels enough.”

United’s boss also said his side failed to work the home goalkeeper – while he had few issues with his side’s two late dismissals.

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Simpson did not totally rule out an appeal against McCalmont’s straight red card for a high challenge on Paul Digby, but contesting the decision appears unlikely.

“Jack Armer’s sending off is a lazy challenge to get that second yellow card,” he said.

“I feel for Alfie a little bit. I have to say it probably is a red card because of the way his foot came up but he had no idea the lad was there and he hasn’t done it intentionally.

“Because his foot’s high, probably because his studs are showing, [the referee] maybe thinks it was excessive force or endangering an opponent, whatever the wording is.

“I’m not sure – I’ll need to look at it again and try and decide.”

Simpson made five second-half substitutions against Mark Bonner’s side but United’s attempted comeback never materialised.

Simpson said the challenge which saw Jack Armer dismissed was 'lazy' (Image: Richard Parkes)

“I just thought we looked tired, that’s why I made the changes early,” the manager added.

“I thought Seani [Maguire] and Butts [Dan Butterworth] looked a little bit tired. Seani has had a lot of games, and Butts had close to a 90 the other day – there’s a whole adrenaline [thing] that goes with getting into the team.

“Unfortunately it didn’t work for us second half so I decided to try and change it. Unfortunately it was one of those days when the changes that I made didn’t have an effect.

“We didn’t have enough [overall]. Even the lads who came off the bench had no impact. I thought Luke Plange had a bit of a go and looked lively, Terry [Ablade] has had one really good run and he blazes it far too high, the next one he has a bit of composure and finds Alfie, and Alfie can’t find the finish.

“So it’s massively disappointing because this has been a real opportunity that we’ve let go.”