A tough, physically strong centre-back,[1] Niccolai initially began his career with Torres in 1963,[2] before joining Cagliari Calcio, where he played from 1964 to 1976, winning the only Serie A championship in the club's entire club history in 1970.

[2] Niccolai played 218 Serie A matches,[2] and is still remembered today for his proneness to score own goals, including some very spectacular ones.

[4] Niccolai made three appearances for the Italy national team in 1970, and represented the team at the 1970 FIFA World Cup, where he won a runners-up medal; he only appeared in Italy's opening group match, a 1–0 win against Sweden on 3 June, as he was replaced by Roberto Rosato in the 37th minute, after sustaining an injury which kept him out of the remainder of the tournament.

[5][6] This led his Cagliari coach Manlio Scopigno to declare: "I could expect everything from my life, but to see Niccolai in international telecast".

This biographical article related to association football in Italy, about a defender born in the 1940s, is a stub.