Kirby started his career when he left school at the age of 16, initially on a YTS scheme at Leicestershire County Cricket Club having been discovered in his native Lancashire.

[1][2] While at Leicestershire he had to overcome sacroiliac instability, a chronic bad back, remodelling his action to learn to bowl fast again, but the county released him after five seasons without making an appearance.

[3] After a net session Yorkshire offered Kirby the chance of some games in the second XI at the start of the 2001 season and after taking 12 wickets in 2 matches he entered into contract discussion but by June was back at his flooring job again.

[3] On 7 June 2001, Kirby received a phone call from Oldham asking if he could come to play for Yorkshire first XI the following day as a substitute for Matthew Hoggard in their Championship fixture against Kent.

[4] On 7 September 2010, Gloucestershire announced that they had released Kirby from the final two years of his contract, after he had requested the chance to play Division One County Championship cricket to push his England claims, turning down the offer of a benefit season.

[22] Having suffered complications from ankle surgery over the 2013 winter, Kirby required a second operation in six months in April 2014 this time on his shoulder, which led to him missing the start of the 2014 season.

[20] After spending a couple of years in executive search firm Michael Page International gaining valuable commercial experience,[28] Kirby was appointed Head Coach of the Marylebone Cricket Club (MCC) at Lord's to commence in April 2016.

[30] In September 2022, Kirby left Somerset to become the new lead bowling coach of the Zimbabwe national cricket team ahead of the 2022 ICC Men's T20 World Cup.