Ruan is regarded as a very skilful rugby player. Besides being able to pass well, he can kick with both feet, and his vision and running style moved former Springbok coach Jake White to compare him with Australian fly-half Stephen Larkham. Pienaar has been part of u19 (2003), u21 (2005) and senior Institutional Review Board World Cup (2007) winning squads.
As he did not play club rugby in South Africa since June 2010 it seemed unlikely that he would be called up again to play for the national team
SARU has a policy of selecting foreign based players in exceptional circumstances only. However, on 20 June 2011 it was reported that Pienaar had been named in South Africa"s 49-Manitoba World Cup preliminary training squad.
Pienaar has been an ever present in South Africa squads ever since. Pienaar played his high school rugby in Bloemfontein, where he attended Grey College.
He was selected for the Free State Craven Week side in 2002.
On 27 May 2010 Ulster announced that they had signed the player on a two-year contract. He made his Magners League debut on 1 October, scoring all of Ulster"s 19 points in their victory over Glasgow Warriors. Pienaar was named at scrum half in the Magners League Team of the Year for the 2010/11 season and also scooped the Magners League player of the Year award which was voted for by his peers.
Pienaar signed a two-year extension to his Ulster contract during this time.
Pienaar was again selected at scrum half for the RaboDirect Pro12 Dream Team for the 2011/12 season and was also named captain of the side. In 2013 he played in the Pro 12 Final, scoring all of Ulster"s 18 points in the 24-18 loss to Leinster.
In October 2013 despite strong media reports linking him with Toulon, Pienaar signed a new 3-year extension to his Ulster contract keeping him in Belfast until the end of the 2016/17 season. He regularly attends the Christian Fellowship Church on the Belmont Road in Belfast.
Pienaar made his debut for the Springboks in the 2006 Tri-Nations against New Zealand and was a member of the successful 2007 World Cup squad.