[8] The following year, Trentin joined the Brilla–Pasta Montegrappa team, winning the Gran Premio della Liberazione,[9] the Trofeo Alcide De Gasperi,[10] and the under-23 Italian National Road Race Championships.

[11] Having initially been announced to ride as a stagiaire in the second half of the 2011 season,[12] Trentin turned professional that August with Quick-Step, making his first start with the team at the Eneco Tour.

[22] He recorded podium finishes in Italian races either side of the UCI Road World Championships, with third at the Coppa Bernocchi,[23] and second in Gran Piemonte,[24] before concluding his season with victory in Paris–Tours.

[27] In May, he won stage 18 of the Giro d'Italia from the breakaway, usurping Moreno Moser and teammate Gianluca Brambilla before the finish line in Pinerolo, having bridged over from a chasing group in the closing kilometres.

[1] Prior to August's European Championships in Glasgow, Trentin's best result of the 2018 season was a third-place stage finish on the opening day of the Tour de Pologne.

[48][49] Having debuted the European champion's jersey at the EuroEyes Cyclassics the following weekend,[50] finishing in fifth place,[51] Trentin took one more victory during the season, winning the penultimate stage at the Tour of Guangxi in October.

[60][61] Held in treacherous weather conditions, Trentin was part of a group of four riders that remained clear on the circuits around Harrogate, but was beaten to the line by Denmark's Mads Pedersen, ultimately finishing with the silver medal.

[63] In the early part of 2020, Trentin finished in fourth place at Omloop Het Nieuwsblad, having been dropped by the leaders on the Muur van Geraardsbergen on the run-in to Ninove.

[75] Having placed second behind teammate Alessandro Covi at February's Vuelta a Murcia,[76] Trentin took his first victory of the 2022 season the following month at Le Samyn, winning the sprint from a lead group of eight riders.

[77] He was scheduled to compete in the Tour de France, but two days prior to the start in Copenhagen, Trentin recorded a positive test for COVID-19, and was replaced by Marc Hirschi.