The former Manchester United assistant spent five years at the Riverside – a spell which saw Boro win the 2004 Carling Cup trophy and reach the 2006 UEFA Cup final. The Teessiders also made some terrific signings under McClaren - scroll down and flick through our gallery to see the best of them:
9. (3rd) Jimmy Floyd Hasselbaink
Just a day after Viduka arrived at the Riverside in the summer of 2004, Hasselbaink also put pen to paper at Rockliffe - and Boro didn't have to pay a single penny for him. After joining on a free transfer from Chelsea, the Dutch frontman added some much-needed firepower to the Teessiders' frontline, helping McClaren's side become contenders in Europe. Photo: Alex Livesey
10. (2nd) Juninho
Undoubtedly the most popular Boro player of modern times. The Brazilian magician rejoined the Teessiders for a third spell under McClaren in 2002 and was instrumental as Boro claimed the Carling Cup trophy and established themselves as a Premier League force. Photo: Shaun Botterill
11. (1st) Gareth Southgate
McClaren's first and most influential signing at the Riverside. A model professional and natural leader, Southgate joined Boro for £6million from Aston Villa in 2001, before becoming the club's first captain to lift a major trophy. The former centre-back then went on to manage the club after McClaren's departure. Photo: Stu Forster