Ryan Porteous admits Scotland have to tighten up after the 4-0 defeat by Netherlands on Friday made it 18 goals conceded in six winless games.

Steve Clarke’s side started well in the first half of the friendly at the Johan Cruijff Arena in Amsterdam until the Dutch took the lead against the run of play five minutes from the break with a powerful Tijjani Reijnders drive.

Scotland striker Lawrence Shankland missed a glorious chance in the 62nd minute when he was through against Dutch goalkeeper Mark Flekken with the Hearts captain clipping the crossbar with his shot.

It started to go really downwards for the Scots 10 minutes later when Georginio Wijnaldum headed in a second before substitutes Wout Weghorst and Donyell Malen added late goals.

Scotland have gone six games without a win for the first time since a run from October 2007 to September 2008 and ahead of the friendly against Northern Ireland at Hampden Park on Tuesday, Watford defender Porteous conceded improvement was required.

He said: “It was disappointing. We were more than in it for long spells.

“We had a number of good chances to get ourselves on level terms or maybe even go in front but ultimately the goals we have conceded have stopped us getting anything from the game.

“It is going to be hard to focus on the positives because of the manner of the result.

“But even if we’re getting beaten in games we can’t concede the goals that we have done. That can’t happen.

“We’ll definitely take a look at them. But up until the 65th minute we’re more than in the game but the sloppy goals and things that we can do better has cost us.

“It’s tough when you’re playing against these teams but we’ve shown that we can do it.

“We are going through a spell right now with six games, we’ve conceded a number of goals and it’s definitely something we want to rectify as a team and, lucky for us, we’ve got another game on Tuesday to try to do that.”

The match, which serves as a first preparation game for the European Championship in the summer, may well have turned out differently had Shankland netted when he was through against Flekken, but former Hibs defender Porteous was understanding.

He said: “I thought he was excellent against arguably the best centre-half in the world (Virgil van Dijk).

“His game has come on leaps and bounds in the last year and he can hold his head up high after that performance.”