Erol Bulut questioned Cardiff’s mentality after an “unacceptable” second-half performance in their 3-1 defeat against Millwall at The Den.

Jake Cooper’s volley put the Lions in front at the break after Michael Obafemi and Yakou Meite traded goals during an entertaining first half.

However, Neil Harris’ side controlled the second half, limiting the Bluebirds to scraps before Duncan Watmore made sure of things in stoppage time with a cool finish past Ethan Horvath.

The result lifts Millwall into 16th, six points clear of the relegation zone, while Cardiff are now 11th with three games remaining.

And Bulut insists his side need to show a winning mentality in their remaining games.

“Millwall at home are a good team, they are working and fighting and I was satisfied with the first half, but with the second half, I have no words for the second half,” he said.

“Nobody can tell me ‘two days before we had a game and we were tired’, Millwall also played a few days ago.

“The main thing is the mentality, how you go in the game, if you want to change this game, if you want to win this game, what you are expecting from yourself individually.

“I can speak only to my players, but the mentality on the field has to change, especially in the second half.

“Consistency is the biggest problem that we have this season. If it was a little bit different then we would be speaking now about different things.

“It was like day and night. In the first half it was clear that the better team was Cardiff but we conceded two goals and the second half was not acceptable.

“If you have these small mistakes in your game then it is difficult to come back.”

The win is a huge boost for relegation-threatened Millwall and Harris believes his side are proving a lot of people wrong.

“Every man and his dog wanted to tell me that these lads can’t play at The Den,” Harris said.

“They do know how to play at The Den and it was a big thing for me to try and galvanise the football club and bring the terrace and the pitch together.

“It’s down to the players when they go on the pitch, so they take the credit and the praise for it.

“Tuesday night against Leicester was a monumental performance from the players and a special evening, but in some ways I’m more pleased with today because to back it up with such a comprehensive performance is testament to the group’s mentality.

“We looked a lot more confident today with the ball and I think if we had scored the third goal at the start of the second half we could have gone on to score four or five.

“It’s important for the football club to stay at this level.”

Millwall’s secured a second successive Sky Bet Championship victory as they eased their relegation worries with a 3-1 win at home to Cardiff.

Jake Cooper’s volley had given the Lions a 2-1 half-time lead after Michael Obafemi and Yakou Meite had traded goals.

And Neil Harris’ side refused to feel the pressure, with Duncan Watmore making sure of victory in stoppage time.

Ryan Longman, who scored the winner against promotion-chasing Leicester in midweek, produced a dangerous delivery that forced a crucial intervention from Dimitrios Goutas during an entertaining start to proceedings at The Den.

Then, in the ninth minute, Burnley loanee Obafemi’s powerful strike beat goalkeeper Ethan Horvath at his near post to score his second goal since arriving in January.

Cardiff captain Joe Ralls took aim from the edge of the box as the visitors looked to get back on level terms, but his shot was straight at Matija Sarkic.

However, it was 1-1 in the 24th minute when Meite nodded Rubin Colwill’s free-kick into the bottom corner from point-blank range.

Will Finnie waved away Zian Flemming’s penalty appeal after the Dutchman went down inside the area, much to the disgust of Millwall’s vocal home supporters.

The Bluebirds had the chance to add insult to injury in the 43rd minute, but Nat Phillips dragged his strike from the centre of the box wide of the right-hand post.

The hosts had the final say of the half, though, with Lions skipper Cooper firing home a thunderous volley after an intelligent flick-on from Longman.

Horvath made two excellent saves in the space of 10 minutes after the break as Millwall looked to double their lead.

First he denied Longman after the Hull loanee let fly with a left-footed shot from outside the box, and then got down quickly to push Obafemi’s goal-bound effort behind for a corner.

Cooper had the chance to give his side some breathing room from a set-piece in the 62nd minute, only to fire his left-footed strike wide of the right-hand upright.

At the other end, Ralls tried again from range only to see his attempt saved by Sarkic before Cian Ashford caused chaos in the Lions box with a powerful cutback towards the penalty spot.

Flemming almost made sure of things with five minutes remaining, but Horvath was up to the task once again.

Cardiff pushed for an equaliser in the final 10 minutes, but Brooke Norton-Cuffy put Watmore through on goal in stoppage time and he prodded the ball past Horvath to secure a crucial win for Millwall.