[2] He made his first-team debut for Chelsea in 2002 as a substitute for John Terry against Aston Villa; his second appearance came as a replacement for Gianfranco Zola in an FA Cup tie.
[2] He made one further appearance in a league match, but fell out of favour after Jose Mourinho became manager and was loaned out to Westerlo and Brentford.
[5] He scored his first goal for the club in a Scottish League Cup defeat against Morton,[6] but he struggled to hold down a first team place, making only 16 appearances.
When John Hughes replaced Mixu Paatelainen as manager before the start of the 2009–10 season, Keenan was told that he was free to find a new club.
[2] He returned to the A-League on loan with Adelaide United for the 2010–11 season as an injury replacement player for injured Nigel Boogaard.