Farmer was unfortunate during his time at Stoke City. He played 163 times for the club and also won England under-23 recognition but he was understudy to both Gordon Banks and Peter Shilton at the club.

It saw him look for loan moves away from the club in search of more regular first-team action and he got it first at West Brom and then with City in December 1974, when he made his debut in goal against Everton at home. It was the first of just two games for the club as he arrived to help out during a goalkeeping emergency to cover the injured Mark Wallington.

He was injured in just his second match however, at Middlesbrough and he was forced to return to Stoke prematurely. Farmer was never to play a professional league game again and went on to play for Northwich Victoria, where he helped them to second in the Northern Premier League, before retiring.