He scored 31 goals in 43 appearances to become the highest scorer in the Scottish Football League in the 1984–85 campaign before he was sold on to Middlesbrough for a fee of £25,000 early in the following season.
He also played for Middlesbrough in the 1990 final of the Full Members Cup and became the first Irish player to score a goal in the Premier League in the inaugural 1992–93 season.
This short international career resulted in the honour of being named in Ireland's 1990 FIFA World Cup squad – though he did not feature in the tournament.
[4] At the age of 18, Slaven rejected an approach from Scottish Second Division club East Stirlingshire and instead joined junior league side Johnstone Burgh.
[8] Slaven joined Scottish First Division club Airdrieonians on a one-month contract after manager Bill Munro needed short-term replacements during an injury crisis.
Still, Rovers chairman Tom Fagan demanded £40,000 to sell Slaven, a high price for a non-professional third-tier player.
[14] Slaven refused to play for Rovers, and was subsequently contacted by a reporter from The Sunday Post, who wrote to 54 English and Scottish clubs on his behalf.
I am 24 years old, and hope that you will at least think over this approach.Yours sincerely,BERNIE SLAVENIn a trial game against Bradford City, Slaven scored and impressed enough to win a move to the club, who secured his services after paying Albion Rovers a £25,000 fee.
[17] Middlesbrough went on a run of five wins in eight games during November and December, but manager Willie Maddren was sacked after picking up just one point in January.
[18] Slaven scored two headed goals to secure a 3–1 victory over Grimsby Town on 4 March in new manager Bruce Rioch's first match in charge.
[20] Middlesbrough entered liquidation during the 1986–87 season, and the Official receiver sacked Rioch and his staff and banned the club from Ayresome Park.
[22] Despite this, Rioch was not afraid to publicly criticise Slaven, and following the club's first defeat of the season by Blackpool on 11 October stated that "...he's overdue a good performance, I wasn't pleased with his form and it's time to show us what he gets paid for".
[23] He played in all the club's 58 league and cup games that season, scoring 22 goals, to help Middlesbrough to secure promotion as runners-up to AFC Bournemouth.
[25] However, Middlesbrough lost to Leicester City on the last day of the season and so finished third behind Aston Villa on goals scored, and needed to secure promotion through the play-offs.
[27] Slaven scored a first-half hat-trick in a 4–3 win over Coventry City on 1 October, shortly after he and several teammates agreed new four-year contracts with Middlesbrough.
[29] In November, Slaven was dropped from the starting eleven for the trip to face Nottingham Forest, which brought to an end his run of 136 consecutive league appearances.
[30] The team struggled in the second half of the 1988–89 season, and when Slaven scored both goals in a 2–1 win over West Ham United at Upton Park on 11 April he ended the club's run of 11 league games without a victory.
[31] Having scored 15 league goals despite playing many games on the left-wing of a relegated team, Slaven was named as the North-East Player of the Year by local journalists.
[36] He went six games without a goal early in the 1990–91 season but broke this run with a hat-trick in a 4–2 win over Brighton & Hove Albion at the Goldstone Ground on 27 October.
[37] However, he was substituted at half-time during a home defeat to Charlton Athletic on 10 November, and reacted badly, leaving the ground and not witnessing the second half.
[41] Todd was sacked in June 1991, and his successor Lennie Lawrence decided to keep Slaven and to play him in a partnership with new signing Paul Wilkinson.
[49] That season Middlesbrough had also reached the semi-final of the League Cup; in the second leg against Manchester United at Old Trafford Slaven equalised to send the game to extra time, before Ryan Giggs scored the winning goal.
[54][55] He was sent off on his debut in a 1–0 win over Leyton Orient at Brisbane Road on 20 March – the first red card of his career – after kicking Adrian Whitbread in retaliation for a bad challenge.
[63] He scored his last goal for the club in a 1–0 win over Premier League Southampton in an FA Cup third round replay at Vale Park on 18 January.
[73] He made his international debut in a friendly on 28 March 1990, and scored the only goal of the game against Wales from a rebound after Kevin Sheedy had a penalty saved by Neville Southall.
"[76] A church-going Catholic, Slaven stated that the highlight of the tournament was the day when the squad met Pope John Paul II at the Vatican.
When the ground was knocked down in 1996, Slaven acquired a section of the fence from the Holgate End and displayed it in his back garden for some years.
[84] The pair also presented shows for NTL's "Boro TV" channel from 1997 until Slaven was sacked in December 2002 after he missed a filming session in protest at the company's habit of failing to pay wages on time.
[87] He announced his intention to stand for the newly created post of Mayor of Middlesbrough in October 2002, but withdrew from the race before the election as his candidacy was a publicity stunt for Century FM rather than a serious attempt to enter politics.
[90] In 2015, Slaven became a Patron of Sporting Memories, a charity that supports former players and older fans living with dementia, depression or loneliness.