Roman Abramovich, Duff made his debut in August 2003 in the Champions League against Slovakian side MŠK Žilina. Chelsea won 2–0 and Duff was described as the "star of the show". He scored his first Chelsea goal on 20 September 2003 in a 5–0 away win against Wolverhampton Wanderers. Duff scored the third Chelsea goal and was named as Man of the match. Duff played 23 games in all competitions for Chelsea in the 2003–04 season scoring five goals. He missed the Champions League semi-finals as Chelsea lost to AS Monaco but was instrumental in securing for Chelsea second place in the Premier League, the club's highest league finish for 49 years as well as being part of the Champions League run, but the season ultimately ended trophyless and with the sacking of manager Claudio Ranieri. The arrival of Dutch winger Arjen Robben and new manager José Mourinho posed a threat to Duff's place in the starting line-up for the 2004–05 season, but an injury to Robben at the start of the season saw Duff as the only available winger. Mourinho, however, did not play Duff in the early part of the 2004–05 season, preferring a more narrow approach. Duff eventually got into the side after four games and, when Robben returned to the side, Duff's versatility saw him move to the right wing and form a wing partnership with Robben. The season proved to be successful for both Duff and Chelsea. He scored ten goals, including a crucial strike in a 4–2 win against Barcelona in the Champions League, while the team won the Premier League title by 12 points from second placed Arsenal, and the League Cup, in which Duff scored the winning goal in the semi-final against Manchester United. He scored three goals in 28 league appearances in the following season as the club retained their Premier League title. Newcastle United In July 2006, Duff agreed terms over a £5 million move to Newcastle United, signing a five-year contract. Duff made his competitive debut in a UEFA Cup second round qualifying first leg match against Latvian side Ventspils on 10 August 2006. He scored his first goal for Newcastle in September that year in a 2–0 victory over West Ham United away at the Boleyn Ground. Duff suffered a knee injury in November that kept him out for four months, during which Newcastle had a bad run