Keith Millen said Carlisle United cannot afford to lose more games through a “lack of discipline”.

The Blues’ efforts at Exeter were undone by Jon Mellish’s first-half red card as they fell to a 2-1 defeat which put them back in the relegation zone.

Millen said he needed to study footage again before commenting fully on the challenge on Archie Collins which saw the midfielder dismissed.

But the manager said his first impression was that Mellish had given ref Will Finnie a decision to make – and that was something the Blues had to avoid.

“I haven’t seen it yet, so I’ll hold my judgement until I’ve watched it back, but what I will say is that when you do that, especially in the modern game, you are making the referee make a decision,” Millen said.

“Now, whether it was right or wrong, you can’t do that in the modern game.

“Once you look like you’re going in two-footed – and I don’t know if that was the case – but the referee all of a sudden has to make a decision. More often than not these days it’s a sending off.

“It’s tough enough as it is and we can’t be doing that. You can’t lose games because of lack of discipline.

“It’s not acceptable and I certainly won’t accept it. I’ll deal with it in-house, because we have to have discipline within the group.”

Mellish’s straight red came towards the end of a first half which had seen United perform well against their high-flying hosts.

Their 10 men then conceded to Sam Nombe and Jake Caprice after the break, Jordan Gibson scoring a late consolation.

United slipped back to second bottom in League Two.

Millen felt there was much to be positive about in the team’s performance even though they left Devon empty-handed.

“The positives were the spirit, the hard work, the togetherness, our shape and understanding of the game,” he said.

“Negatives – discipline, referee’s decisions.

“It’s a tough one because the sending off has such a big impact in the game.

“I feel for the players and the fans. When you put that much effort in you want some reward. We worked so hard, and I thought if there was any justice they should have got something from the game.”

Millen said he was happy with how United had performed when it was 11 against 11, though he admitted they had not made the most of good attacking positions or a string of set-pieces.

He said: “I was really pleased with the way we set up. My only disappointment, and comment at half time, would have been, ‘Let’s be a bit calmer on the ball’.

“I just thought it was a little bit hectic when we won it. The times we did get a pass away we opened them up.

“Our goal came from a great delivery and Gibbo was alive – and it was a difficult finish, good skill.

“We need more of those moments. We had opportunities in the first half when we got down the side of them and into good areas.

“I was disappointed with the quality of our set pieces. We’re doing a lot of work on them. I don’t know what the corner count was but I bet it was double figures. I thought it was a good opportunity for us here.”

Mellish will now face a three-match ban, starting with Tuesday night’s home clash with Harrogate, where Millen will have Callum Guy available after suspension.