2011–2012: Professional debut

In September 2011, Quinzi obtained his first ATP point at the 2011 Mazatlán Open beating the Swiss tennis player Luca Margaroli in the first round. His first best result in ITF Men's Circuit went in 2012 Pozzuoli, where he reached the quarterfinals, but he lost to the Italian player Alessio di Mauro. In September 2012, he reached his first semifinal match in the ITF tournament of Manzanillo, in Mexico, beating, with the score of 6–1, 6–0, the same Yoshihito Nishioka who beat him in the quarterfinals of the 2012 Junior US Open, a week before. In the following two months he also reached the semifinals in other 4 ITF tournaments (Santa Cruz, Santiago, Santa Maria and Lins) often defeating players with a higher ranking and older than him.

On November 23, 2012, he reached is first ITF final in the tournament of Curico, Chile ($10,000, on clay court), defeating Juan Carlos Sáez (world rank No. 464) in the semifinal, but he lost to Guillermo Rivera Aránguiz in straight sets. Quinzi, at the end of 2012, was world rank No. 561.

2013

In 2013 Quinzi obtained his first big professional result in March: in the first ITF Futures tournament he took part, in Bogotá, he soon reached his second career final, beating high-ranked players than him. Here he lost to Carlos Salamanca (three hundred position ahead of him in the ATP rankings) in straight sets.

In April Quinzi officially entered in the Top 500, becoming the youngest player of the ATP rankings among the first 500. He then received a wild card to enter the main draw of the 2013 Rai Open, the first clay court Challenger tournament of the season played in Italy, but he lost in the first round to former Top 100 player Frederico Gil in three sets. The following week he took part to his second ITF tournament of the season, in Sharm El Sheik; he reached his third career ITF final without losing a set. He lost to Mohamed Safwat in three sets. Two weeks later, again in Egypt, Quinzi reached the semifinals of the F6 Futures tournament on clay court, but he lost to Kevin Krawietz.

At the end of may Quinzi played his fourth ITF tournament of the season, in Casablanca ($10.000, clay). After beating the n.1 seed Sergio Gutiérrez Ferrol (former Top 200 on the ATP rankings) in the quarterfinals, and after receiving a walkover in the semifinals, Quinzi reached his fourth career final in an ITF tournament (the third in 2013, in only four tournaments played). Here he won his first career title beating in three sets Lamine Ouahab (former world n.114) and entered, for the first time, the Top 400 of the ATP World rankings.^[9]

In July, Quinzi received a wildcard to join the main draw of the 2013 Guzzini Challenger: here he reached his first win in a Challenger tournament, beating fellow Italian Stefano Travaglia in three sets, but lost in the second round to Flavio Cipolla former n.70 in the world. In August Quinzi took part to two other Challenger tournaments in Italy but lost in the first round to Italian Top 100 players Filippo Volandri and Paolo Lorenzi. In September Quinzi continued playing in ATP Challenger Tour, taking part to some tournaments in South America: at 2013 Quito Challenger Quinzi lost in the second round to eventual semifinalist Giovanni Lapentti; in Porto Alegre, one week later, he entered the main draw as a qualifier and stunned Gastão Elias (world rank No. 129) in the first round, beating him with a 6–3 6–4. Quinzi then reached for the first time the quarterfinals round on an ATP Challenger Tour tournament, defeating Leonardo Kirche 6–2 6–2, but lost in three sets to Pedro Sousa.

In November, in Colombia, Quinzi beat again Gastão Elias with a stunning 6–2 6–0 to reach the second round of the 2013 Challenger Ciudad de Guayaquil where he overtook Bolivian player Hugo Dellien in straight sets. In the quarterfinals he defeated Michael Linzer to reach for the first time the semifinals in a Challenger tournament; he failed to reach the final losing in three sets to former world rank No. 51 Leonardo Mayer.^[10] He finished the season losing to Pavel Krainik in the semifinals of a Future tournament in Mérida, Mexico. At the end of 2013, Quinzi was world rank No. 328.

2014

Quinzi in Oldenzaal (2015)

Quinzi started the season in Zagreb where he obtained his first ATP World Tour victory beating Yannick Mertens in straight sets in the qualifying draw of the 2014 PBZ Zagreb Indoors. Anyway, he lost to Peđa Krstin in the following round. Then Quinzi played in Bergamo having received a wildcard into the singles main draw of the 2014 Trofeo Faip–Perrel where he fell in the first round.

In the following months Quinzi took part to other tournaments around the world, without obtaining any significant result: he lost in the first round of the 2014 All Japan Indoor Tennis Championships; then he was defeated by Argentine player Facundo Argüello in the second round of the 2014 Challenger ATP Cachantún Cup and in the first round of the 2014 Rome Open by Taro Daniel.

In May, after the divorce from his coach Eduardo Medica, Quinzi obtained his best results in 2014, capturing three $10,000 ITF tournaments in three weeks – and winning 15 matches in a row: in Galați, Romania, he beat Romanian Vasile Antonescu, in Safi, Morocco, he beat Hugo Dellien 6–2, 6–2 (capturing the title without losing a set) and then in Casablanca he defeated Gianni Mina in straight sets. With these results he got closer to the ATP's Top 300 rankings.

Later in the year, in August, a wrist injury stopped Quinzi's climb of the ATP rankings. After some disappointing results, in November Quinzi reached the quarterfinals of the 2014 Uruguay Open losing in straight sets to Pedro Cachin; he finished the season in Argentina, where he took part at two ITF events in Mendoza (losing to eventual champion Grzegorz Panfil in the semifinals, and falling in the first round the following week). At the end of 2014 (also because of the injury in the second part of the season) Quinzi was world rank No. 424.

2015

At the end of January Quinzi took part at his first 2015 tournament in Palm Coast: playing on clay, the Italian reached the quarterfinals of the $10.000 ITF event, where he was defeated by eventual finalist Patricio Heras. A couple of weeks later, Quinzi won his fifth Future tournament of his career, beating Federico Coria with the score of 6–4, 6–4 on the green clay of Sunrise (Florida). At the 2015 Argentina Open in Buenos Aires he lost to Thiago Monteiro in straight sets in the second round of the qualifying draw; in March the Italian qualified for the main draw of the 2015 Challenger ATP Cachantún Cup but lost in the first round to Juan Ignacio Londero. Quinzi then obtained a wildcard into the qualifying draw of the Miami Masters, but he was defeated 6–4, 4–6, 6–2 by Thiemo de Bakker.

In April he reached the quarterfinals of the 2015 Tennis Napoli Cup as a wildcard beating the No. 3 seed and world No. 104 Blaž Rola 6–3, 6–1 and fellow Italian Flavio Cipolla (former Top 100 player) in straight sets in the first two rounds; he lost to Marco Cecchinato at the third set tiebreak.

2017

After being awarded a wildcard thanks to a qualifying tournament, Quinzi took part in the first edition of the 2017 Next Generation ATP Finals, held in Milan, Italy.

2021: Retirement

Quinzi retired at 25 years old in July 2021 due to high expectations and competitive stress.^[11][12]

Singles

Singles: 20 (14–6)

Result	W–L	Date	Tournament	Tier	Surface	Opponent	Score
Loss	0–1	Nov 2012	Chile F12, Curicó	Futures	Clay	Guillermo Rivera Aránguiz	4–6, 4–6
Loss	0–2	Mar 2013	Colombia F2, Bogotá	Futures	Clay	Carlos Salamanca	6–7(3–7), 6–7(2–7)
Loss	0–3	Apr 2013	Egypt F4, Sharm El Sheikh	Futures	Clay	Mohamed Safwat	2–6, 6–1, 3–6
Win	1–3	Jun 2013	Morocco F1, Casablanca	Futures	Clay	Lamine Ouahab	7–6(7–2), 1–6, 6-4
Win	2–3	May 2014	Romania F1, Galați	Futures	Clay	Vasile Antonescu	6–3, 2–6, 6–3
Win	3–3	May 2014	Morocco F1, Safi	Futures	Clay	Hugo Dellien	6–2, 6–2
Win	4–3	Jun 2014	Morocco F2, Casablanca	Futures	Clay	Gianni Mina	6–2, 6–3
Win	5–3	Feb 2015	USA F7, Sunrise	Futures	Clay	Federico Coria	6–4, 6–4
Win	6–3	Aug 2015	Netherlands F5, Oldenzaal	Futures	Clay	Jesse Huta Galung	7–5, 2–0 ret.
Win	7–3	Apr 2016	Hungary F1, Szeged	Futures	Clay	Grzegorz Panfil	6–3, 7–5
Win	8–3	May 2016	Bosnia & Herzegovina F3, Kiseljak	Futures	Clay	Dejan Katić	6–2, 6–4
Loss	8–4	Oct 2016	Norway F2, Oslo	Futures	Hard	Lucas Miedler	2–6, 4–6
Win	9–4	Nov 2016	Norway F3, Oslo	Futures	Hard	Casper Ruud	6–4, 6–2
Win	10–4	Jan 2018	Turkey F1, Antalya	Futures	Hard	Marc Sieber	3–6, 6–3, 6–3
Win	11–4	Feb 2018	Egypt F4, Sharm El Sheikh	Futures	Hard	Jaroslav Pospíšil	6–2, 6–4
Win	12–4	Apr 2018	Francavilla, Italy	Challenger	Clay	Casper Ruud	6–4, 6–1
Win	13–4	May 2018	Mestre, Italy	Challenger	Clay	Gian Marco Moroni	6–2, 6–2
Loss	13–5	Jul 2018	Perugia, Italy	Challenger	Clay	Ulises Blanch	5–7, 2–6
Win	14–5	Feb 2020	M25 Weston, United States	World Tennis Tour	Clay	Christian Lindell	3–6, 7–5, 7–5
Loss	14–6	Sep 2020	M25 Jablonec, Czech Republic	World Tennis Tour	Clay	Agustín Velotti	2–6, 1–6

Doubles: 4 (2–2)

Result	W–L	Date	Tournament	Tier	Surface	Partner	Opponents	Score
Loss	0–1	Jul 2013	Recanti, Italy	Challenger	Hard	Adelchi Virgili	Ken Skupski Neal Skupski	4–6, 2–6
Win	1–1	Mar 2016	Israel F6, Ramat HaSharon	Futures	Hard	Lucas Miedler	Aleksandre Metreveli Volodymyr Uzhylovskyi	6–1, 4–6, [10–5]
Win	2–1	Apr 2016	Hungary F1, Szeged	Futures	Clay	Lucas Miedler	Aljaž Radinski Tomislav Ternar	7–6(7–5), 6–2
Loss	2–2	Nov 2016	Norway F3, Oslo	Futures	Hard	Lucas Miedler	Martin Beran Filip Horanský	3–6, 6–2, [4–10]

Singles: 1 (1 title)

Result	Year	Tournament	Surface	Opponent	Score
Win	2013	Wimbledon	Grass	Chung Hyeon	7–5, 7–6(7–2)