Ledley was called into the first team during the 2004–05 season, while still only 17. He made his debut in the League Cup, on 21 September 2004, coming on as a 63rd-minute substitute in a 4–1 win over Milton Keynes Dons He made his league debut the next month, on 16 October, in a 2–0 win over Rotherham United, again coming on as a substitute. Three days later he had his first start for the club in a 1–1 draw with Brighton & Hove Albion, he had several chances to score during the match including a header that hit the woodwork. After the match, Cardiff's goalscorer, Lee Bullock said that Ledley had been brilliant in his first start; creating chances as well as having some himself. Manager Lennie Lawrence said that he thought Ledley hadn't been fazed at all by the occasion and didn't look like he was making his debut. Ledley's first goal for Cardiff came, on 2 November, in a 4–1 victory over West Ham. He brought the ball down from a cross before beating the keeper, Stephen Bywater, with a right foot drive. After this match Ledley's manager and teammates were again full of praise for the youngster. Striker Paul Parry said that Ledley's goal was brilliant and with the way he had been playing, creating so many chances for himself, it was no surprise that he had got his first goal. Manager Lawrence also said that he was impressed with other aspects of Ledley's play. He thought that Ledley had shown incredible maturity during the match, saying that Ledley had, "an old head on a young pair of shoulders". He was also impressed with Ledley's positional play, pointing out how Ledley had tracked back late in the match to cut out a scoring opportunity for West Ham United, when other defenders hadn't seen the danger.