Guerra was then signed with NRL club the Melbourne Storm, but never featured in the first grade squad, mostly being sidelined through injuries.

In the 2013 NRL Grand Final, Guerra played at second-row and scored a try in the Sydney Roosters 26–18 victory over the Manly-Warringah Sea Eagles.

In the post season, Guerra made his international debut playing for Italy in the 2013 World Cup.

[11] In May, Guerra was named as the only change to the Queensland team for game 1 of the 2014 State of Origin series in place of the injured Sam Thaiday.

[16] He made his Australian debut and played his only match in the tournament in the 30–12 loss against New Zealand off the interchange bench at Suncorp Stadium.

[19][20] In round 20, against the Wests Tigers, he played his 100th NRL career match in the 33–8 win at the Sydney Football Stadium.

Despite playing in all 3 State of Origin matches, Guerra was moved to the bench by the Sydney Roosters, and then dropped to reserve grade later in the season.

[28][29] In Round 23 against the Melbourne Storm, Guerra played his 150th NRL match in the 16–13 loss at AAMI Park.

At the end of the season, he was named in the training squad for Italy for the 2017 Rugby League World Cup but later ruled himself out.

[32] In round 1 of the 2018 season, Guerra made his debut for the Newcastle club in their 19-18 golden point extra-time win over the Manly Warringah Sea Eagles.