3. Kevin Keegan
Signed by Liverpool manager Bill Shankly from Scunthorpe United in May 1971, few would have predicted the impact relatively unknown rookie Kevin Keegan would have on the club.
Following Liverpool's struggles in front of goal during a 1-0 Charity Shield defeat to Leicester at the start of the 1971-72 campaign, Keegan was drafted in for his debut in the season opener against Nottingham Forest.
With 12 minutes gone, the 20-year-old scored his first goal for the club and then four minutes later won a penalty for Tommy Smith to convert as the Reds won 3-1.
Keegan would go on to become the club's superstar striker of the 1970s - achieving almost pop idol-esque status inside and outside the game - and he's the man largely credited with bestowing such iconic status upon the LFC No.7 shirt.
During his 323 games for the Reds, Keegan helped add seven major pieces of silverware to the Anfield trophy cabinet, including three league championships and two UEFA Cups.
In 1974, he scored twice at Wembley as Liverpool beat Newcastle United 3-0 to win the FA Cup and three years later, in 1977, Keegan was the talisman of the team which won Liverpool's first ever European Cup, beating Borussia Monchengladbach 3-1 in Rome.