Key succeeded David Fulton at the end of the 2005 season and led the county to a period of one-day success, becoming one of the longest-serving Kent captains. Along with coach Graham Ford, Key "worked out a plan how we were going to become a one-day side".
The highlight of Key's captaincy was lifting the Twenty20 Cup in 2007. In 2008, the county lost in the Twenty20 and 50-over domestic finals, which he described as "the saddest point" of his captaincy.
He will be replaced by a player as equally part of the furniture in Tredwell who has taken 300 first-class wickets for Kent since making his debut in 2001. Key is relieved to be handing over the reins.
"I feel excited about the fact that I don't have to worry about being captain," Key said. "And the things that go with being a captain - the off-the-field stuff like what's going on with your players."
His was a reign of two eras. After recession hit the world in 2008, Kent were not immune to financial troubles "The second half of my term really was like a lot of businesses, like a lot of people around the world where we had to tighten the belts." Experienced players, notably Matthew Walker, moved on and the club became much more dependent upon their young players.
Although Kent gained promotion to Division One of the County Championship in 2009, they were relegated the following season and, in 2011, only Leicestershire finished below them in Division Two.
But Key reflects with satisfaction on how he steered Kent through this difficult period. "There's lots of periods where people wouldn't necessarily think you'd be that proud but actually those little wins along the way in the tough times, when you've got a team of younger players, rather than international players, but you manage to get something out of them when probably no one else thinks you can. They're the moments I'm probably more proud of than anything else."
Last season, Kent defied expectations to challenge strongly for Championship promotion, before finishing third. "At the start of the season we were miles off, we were on nobody's radar, no one thought we were going do very well. At times we were the best side in the second division." Although disappointed at missing out on promotion, Key was satisfied he had left the club in a "decent place" to Tredwell.
But Key reflected that he had somewhat under-performed as a batsman while skipper. In the two years before assuming the captaincy, he averaged 70.00 and 59.84 in first-class cricket. As captain, he has passed 1,000 runs in a season only twice, achieving the feat four times before 2006 and his returns in the last three seasons, an average of 31.30 in 2010, 40.68 in 2011 and 37.95 in 2012, certainly did not reflect his talent.
Key explained: "I took the job on because I wanted it to enhance my England chances and unfortunately one of the disappointments I had is I was never really able to play at the same level. Whereas before I became captain I scored a hell of a lot of runs. Hopefully with a bit of luck I can go back to being one of the top runscorers in the country."
Even if Key is able to do that, he admitted that a 16th Test cap, eight years after his last appearance, is "probably quite a longshot now". But he can reflect with pride on his work as Kent skipper.