Initially a fullback at the beginning of his career, he was later usually deployed as a centre-back, where he excelled due to his anticipation, tackling, marking, and ability to read the game.

Guarneri was known as a "gentleman of the game", as he never received a red-card throughout his career, despite being a tenacious defender.

Although he was unable to win the Coppa Italia throughout his career, he reached the final during the 1964–65 season, narrowly missing out on a treble with Inter.

[1] He made his debut against the defending World Champions Brazil on 12 May 1963, which ended in a 3–0 victory for Italy.

This biographical article related to association football in Italy, about a defender born in the 1930s, is a stub.