John Robertson, who has died aged 72, was once described by legendary Nottingham Forest manager Brian Clough as "the Picasso of our game". Robertson was languishing at the City Ground until Clough arrived in January 1975, releasing the brains and talent that had been hidden behind the Scot's often unkempt appearance to magnificent effect in Forest's great team of the late 1970s and early 1980s.

Indeed, the left-winger was widely regarded as the most influential player in a team that won the First Division title and the League Cup in their first season after winning promotion in 1977-78. This, incredibly, was only the start. Forest followed this up with the even more remarkable feat of not only winning the European Cup in 1979 against Malmo, when Robertson provided the perfect left-wing cross for Trevor Francis' decisive header, but retained it the next year when his goal beat SV Hamburg at the Bernabeu in Madrid.

Robertson was also at the centre of the bitter split between Clough and his long-time managerial partner Peter Taylor in 1983. Clough never forgave Taylor, who was by then managing Derby County, for signing Robertson on a transfer with a fee to be decided by a tribunal, without informing him of his plans. To Clough's great regret, the rift was never healed before Taylor died in 1992, aged 62.

Clough often made teasing mention of Robertson's scruffy appearance and knew about his smoking habit, but regarded it as all worthwhile for the magic he provided with his two-footed touchline-hugging brilliance, measured crossing delivery and his knack of scoring crucial goals. Robertson had played for Scotland at schoolboy and youth level before joining Forest as a teenager in 1970. He had failed to make an impact until Clough's appointment, but the great manager saw something he could nurture.

In his autobiography, Clough wrote: "Rarely could there have been a more unlikely looking professional athlete... scruffy, unfit, uninterested waste of time... but something told me he was worth persevering with and he became one of the finest deliverers of a football I have ever seen." He also wrote: "If one day, I felt a bit off colour, I would sit next to him. I was bloody Errol Flynn in comparison. But give him a ball and a yard of grass, and he was an artist, the Picasso of our game."

Clough was idolised by Robertson, who said: "I knew he liked me but I loved him. I wouldn't have had a career without him." Robertson played in 243 consecutive games between December 1976 and December 1980, and despite the big-name buys such as England goalkeeper Peter Shilton and Francis, Britain's first £1m footballer, he was the player who made Forest tick.

For all the talent elsewhere, Robertson was Forest's fulcrum. In Forest's first season back in the top flight under Clough in 1977-78, Robertson not only played a vital role in winning the title, but also scored the winner from the penalty spot against Liverpool in their League Cup final replay at Old Trafford.

It was not just Clough who recognised Robertson's significance, with former team-mate Martin O'Neill saying: "He was the most influential player in Europe for maybe three-and-a-half to four years." And Forest's captain under Clough, John McGovern, stated: "He was like Ryan Giggs but with two good feet." All this despite Robertson's own admission that he had no pace and could not tackle.

Clough, however, was not bothered about what Robertson could not do, preferring to give him licence to concentrate on what he could do. It was the perfect footballing marriage of manager and player. Two maverick characters working in harmony.

In a famous interview before the 1980 European Cup final against Hamburg, who had England captain Kevin Keegan in their side, Clough was asked about the prospect of their great Germany right-back Manfred Kaltz keeping Robertson quiet. "We've got a little fat guy who will turn him inside out," said Clough. "A very talented, highly skilled, unbelievable outside-left." And so it proved, with Robertson outstanding, deciding the game after 20 minutes, cutting inside to exchange passes with striker Garry Birtles before beating Hamburg keeper Rudi Kargus with his right foot from 20 yards.

Robertson won the First Division title, two European Cups and two League Cups at Forest, playing 386 games and scoring 61 goals, before that acrimonious move to fierce rivals Derby. It is a transfer remembered more for the irreparable division it caused between Clough and Taylor rather than Robertson's deeds. He was now beyond his greatest years, and a return to Forest in August 1985 did not work out.

Robertson won 28 Scotland caps, going to two World Cups in 1978 and 1982. He scored eight goals for his country, including what he called his "greatest ever goal", the winner from the penalty spot in a 1-0 victory over England at Wembley in the 1981 Home International Championship and another in the 5-2 triumph over New Zealand at the 1982 World Cup in Spain.

Latterly, Robertson was a key member of his former Forest colleague O'Neill's backroom team, joining him when he was manager at Wycombe Wanderers, Norwich City, Leicester City, Celtic and Aston Villa. It is, however, for his brilliance under the guidance of the mercurial Clough at the City Ground for which the winger team-mates described as "pure genius" will always be remembered.