#3 Gary Neville and Denis Irwin (Manchester United)
Two of the most important players at Manchester United during their prime, Gary Neville and Denis Irwin, were reliable full-backs who consistently started for the Red Devils.
Neville was a product of the famed Manchester United academy, while Irwin joined the club from Oldham Athletic in 1990 for a fee of £630,000. The two players made over 500 appearances in all competitions for Manchester United.
Neville was a hard-working, aggressive right-back whose determination and leadership ability were well known.
Meanwhile, Irwin was a calmer presence at left-back, with his consistency rated highly by Sir Alex Ferguson. Such were Irwin's performances at left-back that he was a starter for the club even during his 30s.
Irwin departed Manchester United in 2002 after 12 trophy-laden years and joined Wolverhampton Wanderers. Neville, meanwhile, was a one-club man who retired in 2011.
#2 Cafu and Roberto Carlos (Brazil)
Both Cafu and Roberto Carlos enjoyed incredible club careers. But their impact at the international level was extremely visible, as they were mainstays for the Brazil national team for a while.
The full-backs made more than 100 appearances for Brazil and were part of the team that won the Copa America twice (1997,1999) and the FIFA World Cup in 2002.
Carlos was an extremely attack-oriented left-back. He was blessed with strong physical qualities and good speed and is regarded as a legend of Real Madrid. Similarly, Cafu is seen as one of the best right-backs to have played the game, with his intelligence, technical skill and crossing prowess all crucial for both club and country.
Both players retired from national duty in 2006 but went on to represent their clubs for a while. Cafu retired as a player in 2008, while Carlos did so in 2015.
#1 Mauro Tassotti and Paolo Maldini (AC Milan)
The entire AC Milan backline under the management of Arrigo Sacchi and later Fabio Capello earned legendary status. Two of them, full-backs Mauro Tassotti and Paolo Maldini, played an important role in the club's success during that time.
Maldini was a product of the AC Milan academy, while Tassotti was signed from Lazio in 1980. The defensive line of Tassotti, Franco Baresi, Alessandro Costacurta and Maldini is regarded as one of the greatest backlines of all time, with their defensive dominance playing a key role in Milan's incredible trophy-laden stint.
Tassotti was capable of operating as a centre-back when necessary, while Maldini was renowned for his crossing prowess and composure as a left-back. In his later years as a centre-back, Maldini established himself as one of the greatest defenders to have played the game.
Tassotti made 583 appearances in all competitions for Milan, while Maldini, a one-club man, made more than 900 appearances in all competitions for the club.