Mills was brought to the club by Gary McAllister and Eric Black in 2004 and was in charge of a reserve team which finished bottom of a poor FA Premier Reserve League South division,bringing calls for his head.
He left shortly after and joined Notts County but has been back at his beloved Tamworth FC for a couple of seasons.
Speaking to the Birmingham Mail,Mills said: "It was the biggest decision I've ever made in football. I was very happy at Tamworth and we were winning most games. "The offer from Coventry came completely out of the blue - but I decided to go. You have to live by the decisions you make. It's easy to say now I wish I hadn't!"
One player that Mills has fallen out with is Lee Hildreth. The Nuneaton born midfielder,who made one of the shortest ever Sky Blue debut's, was released by City last season and had featured in all Tamworth's matches.
Lee Hildreth
However,after a fall out, Hildreth has opted to join Corby Town where he will team up with former Sky Blues Rikki Bains and Ben Mackey