He made his first team debut, providing an assist for Jackie Henderson in a 3–0 victory over Manchester United at Old Trafford. He scored his first senior goal for the club in a 1–1 draw with Wolverhampton Wanderers, though was criticised by "Daily Mail" journalist Jack Wood for celebrating the goal with an "arms akimbo display of histrionics". New manager Freddie Cox, who succeeded Eddie Lever at Fratton Park in 1958, took the club to relegation with a last place finish in 1958–59 season, though Dougan would miss much of the season with an ankle injury. Dougan was sold on to Blackburn Rovers for a fee of £15,000 in March 1959. He scored on his Rovers debut in a 1–1 draw away to Arsenal at Highbury. He scored twice on the opening day of the 1959–60 season, a 4–0 victory over Fulham, which began a sequence of five wins and a draw from Rovers's first six matches, at the end of which the club were in second-place and Dougan tallied eleven goals, four of which came in a 6–2 victory over West Ham United. Though their league campaign petered out to an eventual 17th-place finish, Rovers reached the 1960 FA Cup Final at Wembley after Dougan scored the winning goal past Sheffield Wednesday in the semi-finals. However, he did not enjoy his time at Ewood Park, and later wrote that "the dourness of the club matched that of the town. I could not shake off the depression that caused me to wake each day regretting that I had to go to the ground. Life was grey and monotonous". This led to him handing in a transfer request the day before the final, which he later admitted was an occasion where his "vanity triumphed over common sense". He was not at full fitness in the final itself, and had a quiet game as Blackburn lost 3–0 to Wolverhampton Wanderers. He opened the 1960–61 season with a hat-trick in a 3–0 win over Manchester United and went on to withdraw his transfer request. Dougan was signed by Aston Villa in July 1961 for a fee of £15,000. He was signed by manager Joe Mercer as a replacement for Gerry Hitchens, who had been sold on to Inter Milan earlier in the summer for £85,000. Teammate Peter McParland later commented that "when Derek came to us at Aston Villa I think it was at a time when he was not taking the game particularly seriously".