Garnett began his career as an apprentice with Tranmere Rovers, where he made his Football League debut during the 1987–88 season.
He turned professional in June 1988 and went on to make more than 100 Football League appearances for the club, during a period that saw Rovers climb from the fourth to the second tier of English professional football, with Garnett making three appearances at Wembley Stadium for Rovers between May 1990 and May 1991.
[2] Garnett spent most of the 1992–93 season out on loan, completely an unwanted hat-trick of being involved in three relegations from the same division during the same season, at Football League Second Division sides Chester City (where he was the final debutant in Harry McNally's seven-year spell in charge[3]), Preston North End and Wigan Athletic.
He remained at Tranmere until March 1996, when he joined Swansea City for £200,000[4] but six months later he returned to north-west England with Oldham Athletic for £150,000.
[5] Garnett spent six years in the Oldham first-team before joining Nationwide Conference side Halifax Town for 2002–03, in a loan move that became permanent.