Failing to break into the first team at Inverness, Kellagher joined Highland League side Nairn County, where he stayed until 2007 when he joined Third Division side, Elgin City for a brief loan spell where he made 1 substitute appearance, before returning to Nairn for another year.
[2] In 2008, Kellacher returned to Inverness, this time for Clachnacuddin, where he stayed for 2 years before officially hanging up his boots in 2010.
[3][4] Kellacher started his managerial career whilst he was still playing for Nairn County, managing Inverness Caledonian Thistle's Under 20s side, from 2006 to 2009, when he was briefly made redundant when Inverness were relegated from the Premier League, before rejoining the role following their promotion in 2010, and remaining with the club until he was promoted to the role of assistant manager in 2018, where he served beside John Robertson, Neil McCann, Billy Dodds, and Duncan Ferguson.
[5] In October 2024, following Inverness going into administration and the sacking of Duncan Ferguson, Kellacher was given the role as head coach,[6][7] with club record goalscorer , captain, and reserves coach, Billy Mckay being given the assistant manager role.
[10] After taking 7 points out of possible 9 against Kelty Hearts, Cove and Alloa Athletic in November, Kellacher won the League One manager of the month award.