Riordan made his debut for Shaanxi Baorong Chanba as a substitute coming on for Fabio Firmani in the 76th minute as they lost 1–0 to Liaoning Whowin, and made his start in a 1–1 draw against Shenzhen Ruby on 14 July. His first goal came when he scored against Chengdu Blades in a 3–1 win on 21 August. He became a favourite player of the fans, but the team performed poorly in the 2011 season. The team manager, Gao Hongbo, criticised Riordan after a defeat by Dalian Shide. Riordan decided to leave the club and his contract was terminated by mutual consent in November 2011. St Johnstone Sky Sports reported that clubs in Italy and Turkey were interested in signing Riordan in January. Riordan trained with Kilmarnock and Blackpool in January, and St Johnstone in March. On 30 March, Riordan signed for St Johnstone until the end of the 2011–12 season. On 21 April 2012, Riordan made his first start in a 2–0 defeat against Dundee United and played 90 minutes in a 5–1 loss against Motherwell on 28 April 2012. The Courier newspaper reported on 15 May that his contract with St Johnstone would not be extended. Riordan agreed in July 2012 to go on trial with an unnamed club in La Liga. Later in July, Riordan trained with League One club Milton Keynes Dons. In August, Ross County made contact with his agent. Bristol Rovers On 27 September 2012, Riordan signed for League Two club Bristol Rovers on a three-month deal. He made his debut on 29 September, in a 2–1 victory against local rivals Exeter City. He made his home debut on 3 October in a 1–0 defeat to Cheltenham Town. Riordan was released at the end of his contract, having made 12 appearances without scoring a goal. Later career Riordan trained with Scottish Championship club Alloa Athletic in November 2013. On 14 February 2014, Alloa signed Riordan on a deal until the end of the season. He made only two substitute appearances in a spell that was affected by an ankle injury. Riordan was released by Alloa at the end of the 2013–14 season. Riordan played as a trialist for Brechin City in October 2014. He was involved in three matches for Brechin, the maximum permitted for a trialist, after which Riordan turned down a contract offer. He then played as a trialist for East Fife