Whenever a teenage creates Real Madrid a historic moment in a crucial European tie against City, it inevitably draws praise and attention.
During his maiden start in the tournament - and fifth game for the team - the young midfielder suitably impressed as the 15-time European champions claimed a 3-0 last-16 first-leg advantage at the Santiago Bernabeu.
The teenager, who also had his club debut in the qualifying round a month ago with a cameo off the bench at Sporting Lisbon, then assisted the Madrid side defeat the English champions in the midweek return to secure a quarter-final place.
Aged 18 years old, the midfielder became the team's most youthful starter to start twice in the Champions League's latter rounds, surpassing star Vinicius Jr's previous mark by a week and a half.
The midfielder is the most recent to emerge from the famed youth system and is quickly establishing himself as one of the manager's most exciting protegees.
He signed for Real from Leganes in 2023, having formerly spent time at Atletico Madrid and Getafe youth teams, and initially featuring for the under-19 side, where he rapidly created a positive impact.
Pitarch progressed to the B team and it was during a friendly match in which they faced the senior squad, then coached by the former defender, where the youngster is said to have drawn the eye of the present manager, who replaced the previous coach in the new year.
Reports would later label the moment as "love at first sight," adding he excelled not only for his skill on the ball, but for the vitality, personality and drive he brought to the team.
In the summer of 2025, former boss Xabi Alonso called up Pitarch to practice with the senior squad and gave him playing time during the warm-up matches.
However, it was Arbeloa's appointment that became the turning point in his development as he came on as a late substitute in each leg against the Portuguese side that set up the clash with Pep Guardiola's team.
"I've dreamed of this every night when sleeping, the first day I started playing football, each day you head to training and each day you have a game," said the player following his first appearance.
"I have just fulfilled my dream with the greatest club in the planet and in the top tournament."
Handed a starting debut in La Liga against Getafe - where he was for several seasons after arriving from Atleti in 2018 - he has retained his spot for the next four as fitness issues to Bellingham and Dani Ceballos provided an opening.
Pitarch has seized it with displays that have defied his age and inexperience.
"He's a extremely fast footballer, and you can observe what he's capable of," remarked Arbeloa. "He's extremely dynamic, with excellent stamina, effort and mobility."
Pitarch's mentality has also stood out to his coach.
"His standout trait is his personality," added Arbeloa. "He constantly demands the possession, and even under pressure, he doesn't feel it.
"I realize fans might be surprised to watch him make his debut in a Champions League match, but he is selected because I had complete confidence in him to do what he usually does.
"Thiago will keep receiving opportunities with the main squad. It is delightful to have a talent like him."
Pitarch was born in Fuenlabrada, in the Spanish capital's community, and was raised deeply involved in the local game, moving through youth setups before joining Real Madrid's famous La Fabrica system.
He possesses both Spanish and Moroccan citizenship, giving him the choice to play for either country at the highest level.
Under Fifa eligibility rules, footballers may represent multiple nations at junior level without being locked in, with the final decision only final once they play in a official full international.
Pitarch has played for the Spanish national team at underage levels, turning out for both the under-19 and under-20 sides, and participated in the 2025 Fifa Under-20 World Cup, where Spain made it to the quarter-finals.
Nevertheless, he has yet to commit to any senior national team, who are monitoring his progress with keen attention.
Speaking recently, Pitarch said: "I have not taken my final decision yet. My situation is great with the Spanish federation, but I will reach a decision soon."
His situation echoes that of other bi-national talents such as Real team-mate Diaz and Barcelona forward Lamine Yamal. Whereas teenage Yamal chose La Roja, Diaz decided to represent Morocco.
For now, Pitarch's focus is on making his mark in the Madrid lineup and repaying his manager's belief.
He played over an hour in the 2-1 victory at the Etihad, which completed a five-one overall triumph and a quarter-final matchup with the German champions.
His substitution by fellow youth graduate in Manuel Angel underscored the coach's confidence in younger players to help the team pursue future success.
After his notable contributions so far on the Champions League, the midfielder is tipped to be a central figure in that.
"Arbeloa treats me the same. We handle it very normally. I attempt not to think about it excessively - I have to earn my playing time on the field," he commented following the win at Manchester.
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