His club career was notably spent with Juventus for whom he made almost 300 league appearances, winning six national titles and two major European trophies.

[9] He gained notoriety for his aggressive man-marking of Diego Maradona in a second-round victory against Argentina at the 1982 World Cup, where he fouled the Argentine star 11 times in the first half,[10][11] and 23 in total,[12] after which Gentile famously quipped, "Football is not for ballerinas!

Italy then faced tournament favorites Brazil in the next second-round group match and won 3–2, in which Paolo Rossi scored a hat trick, while Gentile was tasked with marking Brazilian star playmaker Zico.

[19] A hard-tackling and versatile defender, he was capable of playing both as a man-marking centre-back or "stopper", and as a full-back on either flank, and was particularly known for his tight, heavy, physical marking of opponents, as well as his work-rate, and aggressive challenges.

[27] Although he was not initially known to be the most naturally talented footballer from a skilful standpoint, and was seen as more of a defensive-minded right-back, who mainly sought to break down opposing attacks, he was known for his discipline in training, and showed significant technical improvements throughout his career.

Indeed, he was a mobile and hard-working player, who was also capable of contributing offensively as an attacking full-back in a zonal-marking system, by getting up the flank and providing deliveries into the box for his teammates.

[21][22][23][25][28] Alongside Juventus and Italy teammates Dino Zoff, Brio, Cabrini, and Scirea, he formed one of the most formidable defensive lines in football history.