Barco, who graduated from Boca Juniors' youth system, played senior football at the club for three seasons before moving to England and joining Brighton in January 2024. At the time of his signing, the Seagulls were hopeful that the talented youngster would shine in the Premier League. After securing his signature, Brighton technical director David Weir said in a statement: "We have been aware of Valentin for a long time and have been impressed with the progress he has made at the domestic and international level. We’re delighted to welcome him to the club, and we are looking forward to seeing how he progresses and develops under Roberto.
"He has played predominantly on the left side, as a full-back, wing-back or winger, but also shown his versatility with Boca, playing across the midfield. He is an exciting prospect, but it’s also important we give him the time as he needs to settle and adapt to new surroundings and the Premier League."
However, Barco's stint with the Premier League side did not last long, as at the start of the 2024-25 campaign, he was sent out on loan to Sevilla. Barco then joined Strasbourg on a second loan spell in February 2025, where he finally got to showcase his game and he then permanently signed for the French side in the last transfer window.