[5] Released by Tamworth in 1990, Devlin joined Armitage 90 of the Staffordshire Senior League, but was not there long; in November, Conference club Stafford Rangers paid £2000 for his services, and a 40% sell-on clause was included in the deal.

A lengthy trial with League runners-up Liverpool brought an offer in excess of £100,000 from manager Graeme Souness in September 1991, but Stafford Rangers turned it down.

[20] On 1 March 1996, Devlin and Andy Legg were sold to First Division club Birmingham City for £500,000 the pair;[21] both the "crowd favourites" were out of contract at the end of the season.

[22] Thompson pointed out that until his goal against AFC Bournemouth three days prior, Devlin had gone 13 matches without scoring, that he was a Birmingham boy who had been well aware of the club's interest in him, and that the whole fee would go towards strengthening the team.

[23][22] Devlin scored twice against Wolverhampton Wanderers on 4 March to give his new team their first league win of the year,[24] and by the end of the season had taken his tally to seven from sixteen matches.

[25] Francis dropped him to the reserves after his refusal to agree a new contract and what the Birmingham Post dubbed "a catalogue of tantrum-throwing", preferring the pacy Nicky Forster to partner Furlong.

[42] Devlin's loan was extended to three months, during which he made 11 appearances, scored once, an equaliser as Birmingham came back from two goals down to draw with top-of-the-table Wolverhampton Wanderers, and helped the team finish in the play-off positions;[43] he signed a three-year permanent contract in May.

[45] Devlin was sent off for violent conduct during a pre-season friendly in Scotland; because the referee reported the incident to the Football Association, he was suspended for the first three matches of the new season.

[46] He was selected to start the next, against Leeds United, and after 31 minutes, scored Birmingham's first Premier League goal at their St Andrew's ground with "a sweet right-foot shot that flew beyond [Paul] Robinson from 25 yards (23 m)".

[49][50] New arrivals including Argentina international Luciano Figueroa, top scorer in the 2002–03 Clausura, and club-record signing David Dunn pushed Devlin down the pecking order.

Although he felt he could still contribute at Premier League level, and Bruce did not want him to go, Devlin believed he needed regular football to stand a chance of representing Scotland at Euro 2004.

[51] In September 2003, Devlin turned down an initial loan move to West Ham United in favour of a three-year contract with First Division Watford, managed by Ray Lewington, who were in need of a winger after the death of Jimmy Davis.

Devlin's wages and the £150,000 fee were funded on behalf of the financially struggling club by a "mystery benefactor", who was later confirmed to be former chairman Sir Elton John.

[52][53] He was sent off before half-time for two mistimed tackles in his second match, which Watford lost to a late Derby County goal,[54] but by the end of the campaign, in which the team finished 16th, no outfield player had made more appearances.

[57] He continued in the starting eleven until suffering a hamstring strain during a match in mid-September that was expected to keep him out for a month, but he aggravated the injury and only resumed a place on the bench at the end of November.

[53] Keen to return to the West Midlands for family reasons,[61] Devlin signed for League One club Walsall in mid-January 2006 for the rest of the season.

[65] Devlin had considered retirement after leaving Walsall but was persuaded by Gareth Farrelly to join Bohemians, of which he was player-manager, until the end of the League of Ireland season.

[66] He made his debut as a second-half substitute against Derry City on 7 July, started the next seven matches, scored once, from the penalty spot in a 3–0 win away to Bray Wanderers, and left Bohemians in late August after Farrelly was dismissed.

[68] After a wait for international clearance that manager Mark Cooper claimed would not have happened were Tamworth a bigger club,[69] Devlin played in four Conference matches and then left by mutual consent, as he was unable to commit the necessary time to training and particularly to travelling.

[73] He was released in January 2008 to join another Southern League Premier club, Rugby Town, as player-assistant manager,[74] a role he left for personal reasons after little more than a week.