Barker began his career at Blackburn Rovers under Bobby Saxton's stewardship in 1983, having been Noel Brotherston's boot boy as an apprentice. He had chosen to join Rovers ahead of Manchester United as he felt he had a better chance of breaking into the first-team at Ewood Park. Rovers finished sixth in the Second Division in 1983–84, three places and 13 points outside of the promotion zone. They moved up to fifth in 1984–85, just two places and one point behind promoted Manchester City. Blackburn then dropped down to 19th in 1985–86, just one place and three points above relegated Carlisle United; Barker was voted the club's Player of the Year at the end of the campaign. New manager Don Mackay then rallied them to a 12th-place finish in 1986–87. Barker played for Rovers in the 1987 Full Members Cup Final at Wembley, where Colin Hendry's goal was enough to beat Charlton Athletic 1–0. Blackburn reached the play-offs in 1987–88, but were defeated at the semi-final stage by top-flight Chelsea.
He joined First Division club Queens Park Rangers in 1988 for a fee of £400,000, a club record for both Blackburn and QPR. He made his debut in a 0–0 draw against Manchester United in September of that year. Rangers finished ninth in 1988–89 under Trevor Francis, eleventh in 1989–90 and twelfth in 1990–91 under Don Howe, and eleventh again in 1991–92 under Gerry Francis. Barker helped Rangers post a fifth-place finish in the first ever season of Premier League football in 1992–93, a feat which made them the top club in London. They dropped to ninth in 1993–94, before finishing eighth in 1994–95 under new manager Ray Wilkins. However the sale of top-scorer Les Ferdinand to Newcastle United hit QPR hard, and they were relegated in 1995–96, though Barker did find the net against West London rivals Chelsea. New boss Stewart Houston failed to bring immediate promotion back to the top-flight, as they finished five points outside the play-offs. The club struggled in 1997–98, finishing just one point and one place above relegated Manchester City. After a testimonial match against Jamaica, Barker left Loftus Road for Port Vale. Barker made 351 appearances for QPR in all competitions, scoring 41 goals.
Port Vale
Barker scored on his return to Loftus Road on 5 December 1998, though the "Valiants" lost the game 3–2. He played a total of 25 games in 1998–99, as the club went through a turbulent period by replacing manager John Rudge with Brian Horton. Barker featured just six times at Vale Park in the 1999–2000 campaign, and retired at the of hsi contract in November after picking up an injury.
Post-retirement
After retiring as a player he went on to become a senior executive for the Professional Footballers' Association.
