Every week the BBC Euro Leagues football show panel will select a promising youngster to focus on. This is the first week and our subject is...
The 21-year-old holding midfielder is a regular in the Bundesliga for Stuttgart and has won 11 caps for Argentina's Under-20s, as well as playing in the 2016 Olympic Games.
He started his career at hometown club Estudiantes de La Plata, making his first-team debut in February 2016 and immediately becoming a first-team player - briefly playing alongside Juan Sebastian Veron.
Ascacibar joined Stuttgart last summer for a reported £7m and made 31 appearances in all competitions, helping the club finish seventh in the Bundesliga. He made the fourth highest amount of tackles per 90 minutes in the German top flight.
He finished the season with the joint most tackles of anyone at the club, and the second most interceptions - behind Benjamin Pavard. He had 10 bookings, only one off the divisional record for the season. The club had a 48.1% win record with him in the team and 28.6% in the seven games without.
After only one year at the club, he was handed an extended contract until 2023, with sporting director Michael Reschke saying: "Santi has been an essential element of our squad. He possesses an absolutely exceptional willingness to perform and strength in challenges.
"In addition, he is a true team player, who relentlessly gives his all for the success of the team as a unit. We firmly believe that he can take on a vital leader's role within our team in the future. We consider it extremely important to extend Santi's contract here prematurely."
BBC Euro Leagues football show analysis
German football journalist Raphael Honigstein said: "He's a classic tough-tackling, hard-running defensive midfielder but with real skill as well. He has a tattoo of Diego Maradona on one of his calves.
"They have high hopes for him as he is almost an Esteban Cambiasso-type player who can win the ball and then pass it. He's been instrumental in Stuttgart doing so well.
"Everyone thought they could get relegated last year, then Tayfun Korkut came in in January and they almost finished in the Europa League places. They have had a bad start to the season, losing both Bundesliga games, but he's one everyone is looking at, especially in German football and I'm sure beyond.
"After one year at the club, they already renewed his contract to give him more money and make sure he stays because he's attracting a lot of attention. Remember the name."