#5 Gary Cahill (Bolton Wanderers to Chelsea - £7 million - January 2012)

Gary Cahill has been a stellar servant of Chelsea FC in one of its most successful phases without often getting the credit he deserves. While not the fastest or the most technically sound player, Gary Cahill has been a bulldog on defence ever since his move to Chelsea, forming formidable partnerships with John Terry and later David Luiz.
His CV is adorned with titles including 1 UEFA Champions League trophy, 2 Premier League titles and 1 FA Cup, and all of it as a starter for the club. His no-nonsense style keeps him in the shadows but his record speaks for itself.
He now is the club captain and few can deny his importance to the Chelsea team. As he grows older he might soon be replaced by a younger defender, maybe even Kurt Zouma who he has partnered with in the past, but his contributions to the club make him one of the best defensive players in the club's history.
Best season for Chelsea - 2014/15 (17 Clean-sheets)
Like Matic, Gary Cahill and his defensive abilities were maximized under Jose Mourinho. John Terry and Cahill built the strong foundation for Mourinho's team as they kept 17 clean sheets and conceded only 33 goals throughout the season, (lowest in the Premier League) which set the club up for its 5th Premier League title.