 He joined Carlisle United on a free transfer in June 1999.He let in five goals on his Carlisle debut, a 5–2 defeat away to Halifax Town and did not play again until the following February when he let in another four goals away to Rotherham United.On 24 October 2000, Keen scored for Carlisle with a kick from his own penalty area in the 3–2 defeat away to Blackpool.