manager José Mourinho confirmed that the club had signed Boulahrouz but were waiting for his international clearance to be finalised, before speaking of the potential roles Boulahrouz would have in the side. Mourinho stated "in a short squad and in a country where you can have only 16 players for a match, it’s important to have cover for many positions." On 21 August 2006, Chelsea completed the signing of Boulahrouz. Six days later, he made his Premiership début against Blackburn Rovers. He wore the number 9 shirt, previously occupied by Hernán Crespo – this is an unconventional number for a defender, being traditionally associated with strikers, but was given to him just because it happened to be one of the numbers not currently allocated to a player by Chelsea at the time of signing. Boulahrouz made a promising start to his Chelsea career, featuring prominently in high-profile games against Liverpool and Barcelona. However, Boulahrouz gradually dropped out of favour. Boulahrouz was out for a lengthy period of time after a knee injury, followed by a shoulder injury while playing in an FA Cup tie against Norwich City. Boulahrouz eventually dropped out of contention as the season wound down, with John Terry and Ricardo Carvalho as the first-choice defensive pairing. When Carvalho was injured, manager Mourinho paired Terry with Ghanaian midfielder Michael Essien. Sevilla (loan) Boulahrouz joined Spanish club Sevilla on a year-long loan for the 2007–08 season. However, he played just six games for them and was deemed surplus to requirements. He returned to Chelsea in 2008 but was not given a squad number and made no appearances. VfB Stuttgart On 21 July 2008, Boulahrouz moved to VfB Stuttgart for a fee of around €5 million. He struggled in his first three seasons. Early in the 2011–12 Bundesliga season, however, Khalid became a regular in the starting line-up. The 29-year-old defender had his 100th cap in the top German league on 17 September 2011 at SC Freiburg. Two weeks later, Boulahrouz scored his first goal (only his second in the Bundesliga) for Stuttgart on 30 September 2011. His goal came in the 69th minute of a 2–0 win over 1. FC Kaiserslautern. In May 2012 VfB Stuttgart announced that his expiring contract would not be extended. Sporting CP On 18 July 2012, Boulahrouz signed a two-year contract with Sporting Clube de Portugal. He made 11 league appearances for the club,