Monreal left Real Sociedad at the end of his contract after missing the 2021-22 season due to injury.
The left-back, who won 22 caps for his country, on Tuesday announced that his 16-year professional career is over.
He posted on Instagram: "Thirty-six years playing football, 16 as a professional. Squeezing my body and taking it to limits that I would never have imagined.
"My knee sends me a message… loud and clear; I cannot continue! Do I get mad? NO! I listen to it and accept the situation and thank it for everything.
"A stage is over. Another starts. I'm happy and feeling good. One more time… I FEEL GOOD!!! And that gives me peace of mind.
"Life is a gift and I like to be grateful. Thank you Osasuna, Spain, Malaga, Arsenal, Real Sociedad for letting me cross your paths. What good years…."
Monreal started his career at Osasuna and joined Malaga before spending over six years with Arsenal, winning the FA Cup three times with the Gunners.
He returned to his homeland with La Real in 2019 and lifted the Copa del Rey trophy the following year after a 1-0 victory over Athletic Bilbao.
Using Opta data, we have already examined some of the worst attacking and passing numbers from 2019-20, so now it's the turn of the defence.
We have analysed nine metrics for defenders to have featured in at least 10 league games this season, thereby giving us a good summary of those whose defending could use some improvement.
The metrics include success rates in duels, tackling and aerial challenges, errors leading to shots and goals and how many times a player has been dribbled past by an opponent.
As always when it comes to data, context is key. For success rates in duels, tackling and aerial challenges we have only included players who have completed 20 actions in each category, which accounts to two per game.
The below therefore provides a good indication on where improvement is needed, and there are a few surprising names…
THE WORST DEFENDING STATS IN EUROPE'S TOP-FIVE LEAGUES 2019-20:
BUNDESLIGA:
Most tackles lost: William (29)
Worst tackle success: Alexander Hack (40.91 per cent)
Most errors leading to goals: Robin Koch (3)
Most errors leading to shots (including goals): Robin Koch (3)
Most dribbled past by an opponent: William (32)
Most duels lost: Stefan Lainer(125)
Worst duel success: Julian Ryerson (35 per cent)
Most aerials lost: Robin Koch and Sven Bender (56)
Worst aerial success: Christian Gunter (22.86 per cent)
LALIGA:
Most tackles lost: Pervis Estupinan (34)
Worst tackle success: Nacho Monreal (40 per cent)
Most errors leading to goals: Joseph Aidoo and Sergio Ramos (2)
Most errors leading to shots (including goals): Pervis Estupinan (5)
Most dribbled past by an opponent: Marc Cucurella (35)
Most duels lost: Marc Cucurella (167)
Worst duel success: Daniel Carrico (40.3 per cent)
Most aerials lost: Didac Vila (55)
Worst aerial success: Xavi Quintilla (25.71 per cent)
LIGUE 1:
Most tackles lost: Boubacar Kamara (33)
Worst tackle success: Lionel Carole (34.78 per cent)
Most errors leading to goals: Sofiane Alakouch, Timothee Kolodziejczak and Stefan Mitrovic(2)
Most errors leading to shots (including goals): Wesley Fofana, Alexander Djiku and Malang Sarr(4)
Most dribbled past by an opponent: Arturo Calabresi (42)
Most duels lost: Issiaga Sylla(161)
Worst duel success: Colin Dagba (40 per cent)
Most aerials lost: Pablo Martinez (59)
Worst aerial success: Hamza Mendyl(17.39 per cent)
PREMIER LEAGUE:
Most tackles lost: Ricardo Pereira (50)
Worst tackle success: Calum Chambers (38.46 per cent)
Most errors leading to goals: Jan Bednarek (3)
Most errors leading to shots (including goals): Jan Bednarek, Tyrone Mings, John Egan, Davinson Sanchez and James Tarkowski (4)
Most dribbled past by an opponent: Ricardo Pereira(53)
Most duels lost: Ricardo Pereira (215)
Worst duel success: Benjamin Mendy (37.38 per cent)
Most aerials lost: Ben Mee (84)
Worst aerial success: Max Aarons (26.09 per cent)
SERIE A:
Most tackles lost: Matteo Darmian (32)
Worst tackle success: Andrea Cistana (40 per cent)
Most errors leading to goals: Jhon Chancellor, Fabio Lucioni, Jose Luis Palomino, Alex Sandro (2)
Most errors leading to shots (including goals): Fabio Lucioni (5)
Most dribbled past by an opponent: Stefano Sabelli (40)
Most duels lost: Giovanni Di Lorenzo (126)
Worst duel success: Hans Hateboer (40.63 per cent)
Most aerials lost: Mattia Bani (57)
Worst aerial success: Jeremy Toljan (28.00 per cent)
AND THE TOP NINE:
Most tackles lost: Ricardo Pereira (50)
Worst tackle success: Lionel Carole (34.78 per cent)
Most errors leading to goals: Robin Koch and Jan Bednarek(3)
Most errors leading to shots (including goals): Pervis Estupinan and Fabio Lucioni (5)
Most dribbled past by an opponent: Ricardo Pereira(53)
Most duels lost: Ricardo Pereira (215)
Worst duel success: Julian Ryerson (35 per cent)
Most aerials lost: Ben Mee (84)
Worst aerial success: Hamza Mendyl (17.39 per cent)
