Simpson joined the Dons as a 16 year old from youth side Middlefield Wasps in early 1978, when Bill McNeill was in charge, and was pitched into the reserve side almost as soon as he arrived at the club. He came on leaps and bounds, and in the early weeks of the 1978-79 season he quickly impressed new Dons boss Alex Ferguson. Neil was rewarded with a first team outing as a substitute in the 7-1 League Cup demolition of Hamilton Accies at Pittodrie on 11th October 1978. This taste of first team action gave him a hunger for bigger things, and the enthusiastic Newmachar lad returned to the reserves to continue his development with a new sense of purpose.

As the Dons swept to the 1980 Scottish League title with a midfield of Strachan, McMaster, Jarvie and/or Watson, it looked as though young Simmie may have a lengthy wait to make his first team breakthrough. However, fate intervened in the shape of a rash of injuries to top team players during the 1980-81 season. John McMaster (who would surely have featured as a Dark Blue Don in this series but for injury) and then Gordon Strachan were the most prominent of the long term casualties. The latter's stomach muscle tear opened the door for Simpson, and the youngster made the most of it.

With each game Simmie visibly grew in stature, until by the end of the 1980-81 season with a mere 15 first team starts under his belt the competitive midfielder had given Alex Ferguson the happy problem of a surplus of midfield men to accommodate in his starting line-up. Over the 1981-82 season Simmie established himself in a young emerging midfield of Strachan, Simpson and Cooper. His tireless displays and ability to win the ball consistently in 40-60 situations, plus a superb temperament, won him the affection of the Pittodrie faithful. Simmie was much more than a big hearted ball winner, however, a feature of his play was that he could simultaneously snuff out opposing playmakers, such as Celtic's Paul McStay, yet contribute significantly in supporting attacking moves. His appetite for the game seemed endless, and his stamina was nothing short of miraculous. Lung bursting surges up the park at the end of a gruelling 90 minutes were not uncommon when Simmie was at his peak.

He was a big influence on the Dons Scottish Cup wining side in 1982, and was the engine in the key midfield area as the Dons marched to European glory over the 1982-83 campaign. Neil's impressive displays for the Dons earned him a call-up to the Scottish under-21 European Championships and he was simply outstanding as the Scots beat Italy over two legs in the quarter final before going out to England in the semi. In the second leg of the quarter final at Pittodrie, he did such a good job in the middle of the Park that Italian youngster Bergomi lost his cool and was red carded after being beaten by Neil in yet another challenge. Just three months later the same Bergomi played a part in the Azzurri's 1982 World Cup triumph in Spain. Three further under-21 caps followed during the momentous 1982-83 season, and Simmie's contribution at this level made his promotion to the full Scotland squad inevitable, although the timing could have been better.

With the euphoria of Gothenburg and another Scottish Cup triumph still in the air, Neil was called up for the British Championship opener against Northern Ireland at Hampden on 24 May 1983. Once again, in what had almost become an annual event, manager Jock Stein used the Irish fixture to experiment, Simpson was the only new cap named, but Dave Narey and John Wark were the only regulars picked. The rest of the team consisted either of payers returning after a long absence from the international limelight, such as Andy Gray and Paul Hegarty, or relatively inexperienced players with just one or two caps, among them Richard Gough and Charlie Nicholas. Neil was understandably pleased with his elevation to the Scottish international squad, but the match came just four days after a draining Scottish Cup final, and the mental and physical toll on the Dons player was all too evident. Simmie did not really do himself justice against Northern Ireland, and was replaced after an hour - as originally planned by Stein - by clubmate Gordon Strachan.

Despite starring in an Aberdeen side that clinched a League and Scottish Cup double over the 1983-84 season, Simmie did not get another cap call for over 12 months. Then he was named in a Scottish team to provide opposition in a friendly match against host nation and tournament favourites France in the immediate pre-1984 European Championship Finals period. Simpson started on the bench and had to watch as Platini and Giresse turned on the style to put France in an early 2-0 lead. He was introduced in place of Gordon Strachan at half-time to join Jim Bett and John Wark in midfield but, despite a typical battling performance from Neil, there was little chance of Scotland turning things round. Surprisingly - to Dons fans anyway - Simmie slipped out of the full international picture over the following three seasons, although it must be said that injuries were a factor, particularly towards the end of the 1985-86 season.

The next campaign was even more frustrating in terms of injury, with Simpson sidelined after an injury in the early moments of the opening match at Tannadice on August 9 until the beginning of March 1988. But a miserable season in which Neil played only 13 out of a total of 60 Dons first team games had a silver lining when Andy Roxburgh gave him a surprise call-up to the Scotland side to face England at Hampden on May 23. On the day Simmie was the best Scot on show, as his boundless energy and industry blunted the threat of Glenn Hoddle, Bryan Robson and company in the English engine room. Despite a disappointing 0-0 scoreline it looked as though Simpson might be back as a force to both club and country. Injury problems, however, had virtually become a way of life from the unfortunate midfielder and he missed a large part of the 1987-88 season before making an end of the season comeback.

Once again he finished a frustrating club campaign with a late call-up to a full Scotland squad. Simmie sat out the Rous Cup opener against Columbia on 17th May 1988 but three days later was named in the Scotland side to face England at Wembley in what was to prove the last of the annual fixtures between the two sides played south of the border. The Scots battled hard, but lost 1-0 and Neil was replaced by Celtic's Tommy Burns as the Scots chased the game in the second half. Any chance of Simpson furthering his international career was effectively ended by "that" incident with Ian Durrant in a league fixture on 8th October 1988, although in truth his own battle with injury was a bigger factor as a bad knee injury on September 1989 took its toll.

The following year Simmie moved to Newcastle United, but he was afforded few chances to make his mark in the first team, and he returned north to Motherwell in August 1991. At Fir Park he was a first team regular for two seasons, and was still well received at Pittodrie on visits to the North East. In October 1993 after a brief flirtation with Cove Rangers, Neil was appointed SFA Community Development Officer for the North of Scotland. Neil still works at Pittodrie as a Community Coach.