Queensland Reds Horwill made his Super 14 debut against arch rivals the
New South Wales Waratahs in the first game of the 2006 season, after not even being included in the Reds original squad. Horwill captained the
Queensland Reds to a season victory in the 2011 in the
Super Rugby competition, his sixth season played at that level Overall, Horwill played more than 129 times for the
Queensland Reds, including 116 Super Rugby caps for the Reds. When his departure was announced the Queensland Rugby CEO Jim Carmichael described him as "one of the great modern-day sporting treasures of Queensland."
Harlequins On 17 December 2014, it was announced that Horwill had signed a three-year contract with
English Premiership side
Harlequins. He made his competitive debut in Quins' season opener against
Wasps FC on 16 October 2015 and immediately established himself as a first choice in the team. He scored his debut points with a try in the match against
Saracens F.C. on 9 January 2016. He also captained the side in the absence of Quins' England players. Horwill played his last season for Harlequins in 2018-19 before retiring from professional rugby. He then played for
Cambridge University R.U.F.C. in the 2019 Varsity match. ==International career==