Image copyright PA Image caption Andrew Robertson played for Liverpool against Atletico Madrid in the pre-season Audi Cup

"If I don't play I'm always annoyed, but I've learned over the years to put that frustration into being better in training instead of taking the hump."

That attitude has served Andrew Robertson well in his developing career.

From being discarded by his boyhood heroes Celtic to signing for Liverpool, the left-back has shown a determination to improve. It has taken him from the amateur ranks with Queen's Park to Anfield in four years.

A Spider, a Terror, a Tiger

Whether with Queen's Park in Scotland's fourth tier, Premiership Dundee United or Premier League Hull City, he has always made the left-back berth his own.

Yet for the first time he is having to fight his way into the first team, with Liverpool boss Jurgen Klopp preferring Spain international Alberto Moreno, a £12m signing in August 2014, to the 23-year-old Scot.

Image caption Andrew Robertson determined to fight for Liverpool place

Robertson was man of the match for the Reds against Crystal Palace on his league debut on 19 August and has since played in the 1-1 home league draw with Burnley and the 2-0 League Cup defeat by Leicester on 19 September.

This season, he has played more games for Scotland (four) than competitive matches for his club.

"I've just got to be patient and hopefully it will turn and I'll get more game time at Liverpool," Robertson told BBC Scotland during the international break.

"I am realistic, I know how much quality is in the Liverpool squad. The three games I've played I have been really happy with my performances.

"I need to be patient and not let my head drop and, if I keep doing that, hopefully it will work out for me, which I am confident it will."

Robertson explains that Klopp calls the left-back role "a specialist position" and that he prefers his substitutes to be able to cover more than one area.

Image copyright SNS Image caption November 2014: Robertson scores his first international goal, against England in a 3-1 defeat in a friendly

"For me and Moreno, if we start, great; if we don't, realistically we will be in the stand or not travelling," he said.

"We have attacking people on the bench who can come on and change the game, which we usually need.

"James Milner had played left-back all last season and a lot people on the outside probably thought Moreno was finished at Liverpool, but he has worked really hard in training to get everything right. He has played well since he has been in there.

"It has been frustrating for me because my signing has probably lifted him but I believe that it has given Liverpool two good left-backs."

Robertson's journey to Anfield - Celtic let him go

"At the time it was devastating," says Robertson of being released by Celtic at 15.

"I've never hidden that I am a massive Celtic fan.

"At that young age you don't really know how to deal with it. Looking back on it, it was the best thing that happened to me. If they did give me a contract I could have got lost in the youth system.

Image copyright SNS Image caption Robertson holds the 2013-14 PFA Scotland Young Player of the Year trophy

"It gave me the motivation to succeed at Queen's Park and I kept on using that motivation.

"I've played with people at Dundee United, Queen's Park and Celtic who probably were more technically gifted who are not playing today or who are playing junior football, which they are quite happy with."

Working nine to five, training at night

Robertson trained with amateur club Queen's Park in the evenings and got a day-time job in the commercial offices at Hampden, Scotland's national stadium and the Spiders' home ground.

He maintains that juggling the two roles "has helped massively to appreciate everything I have".

He said: "My first season at Queen's Park, I was hopeless. They were probably thinking, 'how was this boy at Celtic?'

"Then just one game made it all spark. I got my confidence back and I kicked on in my second season and from that moment I have never looked back.

Image copyright SNS Image caption October 2012: Robertson got used to playing in front of big crowds with Rangers being in the Third Division during his time at Queen's Park

"There were two teams at Under-17 at Queen's Park. I was playing left midfield in the second team as such.

"Our left-back went up and played with the better team and I played at Stirling Albion away on a Friday night and I ended up scoring.

"That was the moment Queen's Park maybe looked at me more as left-back than a left mid. It all turned and my confidence went sky high.

"I got big-game experience because Rangers were down in the Third Division. I think we had 40,000 at Hampden because of the Rangers fans."

To Tannadice and then Hull City

His performances in the black and white of Queen's Park attracted the Dundee United boss Jackie McNamara, a former Scotland full-back.

Within nine months of signing, aged 19, for the Terrors in the summer of 2013, Robertson made his Scotland debut in a friendly against Poland. He made 46 appearances in his first season with United, scoring five goals, and was voted PFA Scotland Young Player of the Year.

"I loved every minute at Dundee United. From the first game I never looked back," he said.

Image copyright SNS Image caption April 2014: Dundee United's Robertson shields the ball from his Scotland team-mate, Celtic midfielder Scott Brown

"Jackie was massive for me. He kept giving me advice, from a top full-back in his time. I will always look back on the year at Dundee United with fond memories."

Robertson's rise continued when Steve Bruce took him to Hull for £2.85m in July 2014 after only one year as a full-time player, and from there he made the £8m switch to Anfield in the summer.

"I enjoy looking at my journey, seeing where I was at Queen's Park working nine-to-five jobs to where I am today," he says.

"There is no easy way to become a professional footballer. Everyone has had a different journey but mine has a wee bit more exciting.

"Football is a team sport and you need to be a team player but you need to be self-driven as well.

"If I go into training and I don't think I'm quite at it I'll be annoyed at myself. That's the way I have always been, whether it was at Queen's Park or Liverpool; it doesn't make a difference.

"I'm still the same person. I know I need to do a lot to improve. I've had a few dips but I've had three years of success and it probably turned me into a man and improved me as a footballer."

Grounded and benched, though you suspect the latter won't be for long.

Andrew Robertson was talking to Rob Maclean.