Early career and loan spells in 2009 Product of Defensores de Cambaceres lower divisions, Pratto joined Argentine club Boca Juniors in 2006, after a recommendation by
Martín Palermo. Once in the
La Boca-based team, he was sent to the team's fifth division, where he scored more than 20 goals and formed an attacking partnership with
Óscar Trejo. In June 2007, he was loaned to Tigre, but mostly played for the
reserve team in their first season.
Leandro Lázzaro's departure to Estudiantes, however, allowed Pratto to break into the starting eleven and challenge the possibility of being the team's first choice striker. Following Lázzaro's absence, Lucas played ten
2008 Clausura games and scored one goal against
San Martín de San Juan, which was his side's winning goal in a 2–1 home win at
José Dellagiovanna. On 2 August 2008, Pratto joined Norway's Lyn Fotball on a free loan from Boca, after being recommended by the scout
Terje Liverød who helped with the negotiations. On 15 August, Lucas made a goalscoring debut during a 3–1 defeat against
Molde FK in a
Tippeligaen game as a 71st-minute substitute. Between 2008 and 2009 Pratto made 21 league appearances and scored four goals for Lyn. He then returned to Argentina in mid-2009 to join Boca's first-team squad, then coached by
Alfio Basile. In the Chilean club, Pratto scored in his debut against
Everton in a 1–1 league draw at
Viña del Mar. At first, Lucas was heavily criticized for his bad shape at the
Las Condes-based team, but key goals in the end of the season against
Universidad de Chile and
Cobreloa helped Católica achieve their 10th
Campeonato Nacional title. He had an impressive season start in 2011 when he scored six
Copa Libertadores goals (including a brace against
Grêmio, in a historic 2–1 triumph at
Brazil) and six league goals, which allowed him be sold by Boca to
Italian Serie A side Genoa for a
US$2,4 million fee.
Genoa Pratto joined the Genovese club on 30 June 2011, being described months before by the club's president
Enrico Preziosi as the team's new
Diego Milito. He officially debuted as a starter during Genoa's first
2011–12 Coppa Italia game against
Nocerina in a 4–3 home win, in which he scored his side's second goal after an assist by
Kévin Constant. His Serie A debut was on 11 September in a 2–2 draw with
Atalanta for the league's first matchday, and his first goal came on 18 December in a 2–1 victory over
Bologna, the match-winner at the 85th minute. His second goal for Coppa Italia was on 24 November against
Bari in a 3–2 victory, where once again he scored the match's winning goal, now after an impressive header in the 115th minute during
extra-time. Pratto made an attacking partnership with
Rodrigo Palacio, but coach
Alberto Malesani, by whom he was selected for the first squad, was fired in December 2011. Since that time Lucas failed to play the rest of season, being relegated to the bench by the team's next coaches (
Pasquale Marino, the same Malesani and
Luigi De Canio).
Vélez Sarsfield match against
Peñarol On 7 February 2012 it was reported that Pratto had joined
Vélez Sarsfield in a season-long loan deal, with the option to be fully signed by the Argentine club. After a decent first season with the
Liniers side, in which he played 20 times and scored 4 goals, Lucas became a starter during Vélez's
2012 Torneo Inicial championship-winning campaign. Pratto made a partnership with
Facundo Ferreyra, and played a key role appearing in all 19 games and scoring seven goals. In January 2013 it was reported that Vélez had come to an agreement with Genoa for the definitive purchase of the player on a three-year contract. On 29 June 2013, Lucas scored the match winner in the Superfinal, the match that concluded the
2012–13 Primera División season, as Vélez defeated
Newell's 1–0 and were crowned Super Champions. At the end of the year Pratto was selected as Vélez's best player of the season. In the start of 2014 he won the
Supercopa Argentina with his club, and was the top goalscorer of the
Torneo de Transición, with 11 goals. For his performances Pratto was once again selected as Vélez's player of the year, and was honored with the
Olimpia de Plata award as Footballer of the Year of Argentina, chosen by Argentine sports media as the best player in the local league. Pratto made his unofficial debut and scored his first goal for Atlético in a pre-season friendly against
Shakhtar Donetsk, which his new team won 4–2. Pratto also scored in his first official match for the club, against
Tupi, for the 2015
Campeonato Mineiro, as well as in his debut in
Copa Libertadores for Atlético, scoring the winner in a 1–0 away win against
Independiente Santa Fé. In the second leg of the
Campeonato Mineiro semifinals against fierce rivals
Cruzeiro, Pratto managed to score a brace with two assists by
Guilherme, one of the goals an impressive volley, and helped his team make a 2–1 comeback after trailing in half-time. Atlético were eventually crowned champions of the competition, with Pratto finishing with six goals and being selected for the team of the tournament and as its best player. In July 2015, Pratto became Atlético's highest-ever foreign goalscorer and scored his first-ever hat-trick, with all three goals coming in the first half of a 3–1 home win against
São Paulo. He still holds this record as the club's highest-ever foreign goalscorer, with 42 goals.
São Paulo On 10 February 2017, Pratto signed a four-year contract with Brazilian club
São Paulo FC. The transfer totalled around €12 million, with the
São Paulo-based club paying approximately €6 million for 50 per cent of the player's rights. According to Carlos Augusto de Barros e Silva, São Paulo's president, the club would acquire up to 95% of the rights in the future. Atlético Mineiro president Daniel Nepomuceno stated that payment for the remaining shares would occur within three years. He netted in his debut for
Tricolor, in a 2–2 draw against
Mirassol, and, three days later, he scored twice in his second match for club, in a 3–2 victory against
São Bento. Pratto, along with his compatriot
Calleri, is the only debut player at the club to score in his two first official matches. On 9 July 2017, Pratto lost a penalty kick in a 3–2 loss of
São Paulo FC against rivals
Santos FC. At the end of this match, he was seven consecutive games without scoring any goal.
River Plate On 8 January 2018, São Paulo confirmed the selling of Pratto to
River Plate for €11.5 million, becoming River's highest ever transfer acquisition. Pratto scored two goals in the
2018 Copa Libertadores finals against
Boca Juniors, once in each leg, helping River to the title.
Feyenoord On 1 January 2021,
Eredivisie club
Feyenoord announced the signing of Pratto on loan for the remainder of the
season. He made his debut nine days later, in a
Rotterdam derby against
Sparta in the
league, won 2–0 by Feyenoord. On 9 May, in a 3–0 league defeat to
Ajax, Pratto suffered a fracture in his right ankle when challenging for the ball; he underwent surgery on the same day, with an expected recovery time of four to six months.
Return to Vélez Sarsfield On 27 August 2021, Pratto returned to
Vélez Sarsfield, with a contract valid until December 2023. Pratto made his debut on 30 October 2021 in a substitute appearance against
Banfield, coming on for
Agustín Bouzat, where the match finished 2-1 to Banfield. His first goal came on 23 November 2021, against
Argentinos Juniors, to make the score 2-0 to Vélez. However, he was released from the club in June 2023, due to bad results.
Defensa y Justicia On 26 July 2023,
Defensa y Justicia signed Pratto on a one-year deal. He made his debut on 1 August 2023 against
Emelec in a 2-1 win in the
Copa Sudamericana, providing an assist for
Nicolás Fernández. He made his league debut and scored his first goal in a 2-2 draw against
Godoy Cruz on 12 September 2023.
Olimpia On 13 January 2024, Pratto joined Paraguayan club
Olimpia.
Sarmiento On 5 July 2025, Pratto returned to Argentina to join
Sarmiento, signing a contract until the end of 2026.
Coquimbo Unido On 6 January 2026, Pratto returned to Chile and signed with then Chilean champions
Coquimbo Unido. == International career ==