On 12 April 2008, Sinclair faced his first club, Blackpool, for the first time since leaving them fifteen years earlier. He scored Cardiff's second goal in a 3–1 win; however, he refused to celebrate his goal. On 17 May he made an 86th-minute substitute appearance in the 2008 FA Cup Final at Wembley Stadium, which Cardiff lost 1–0 to Portsmouth. However, four days later it was announced that his contract would not be renewed for the forthcoming season and he was released.