The Spanish defender was drafted in due to injury to Kieran Gibbs.
It looks like Arsenal may be without the in form Kieran Gibbs against Burnley tomorrow. The England international is struggling with a hip problem. Despite Arsene Wenger claiming the Arsenal left-back would feature in the game - Gibbs did not take part in Arsenal training this afternoon.
But he was seemingly replaced by a young left-back hoping to follow in the footsteps of a recent graduate.
Hector Bellerin has recently become a member of the Arsenal first-team. The former Barcelona player is yet another to come through the ranks in Catalonia and get his chance with The Gunners.
Following in his footsteps is Julio Pleguezuelo.
The 17-year-old signed a professional contract at the club in April after first arriving at the club from Barca in the summer of 2013.
He was snapped in action with the Arsenal first-team today, going head-to-head with £16 million striker Danny Welbeck at London Colney.
He will be hoping to make his name in the under-21 side before slowly making his way into the Arsenal first-team - as more than a simple Kieran Gibbs stop-gap in training.