The 19-year-old academy graduate delivered another technically and tactically assured display, with and without the ball, leaving Hansi Flick and his team-mates thoroughly impressed.
La Masia has a new star on its hands - another player born in 2007 to break through at Barcelona, joining Lamine Yamal, Marc Bernal and Pau Cubarsí in that group.
"I appreciate a lot what I see from him. I'm surprised he can also play on the left. He's always focused, and tactically he's very good. I'm very happy, he's a really top player," Flick said after the Athletic Club win.
"I'm a little surprised by his composure, by how he plays... it's great. Technically, he's at a high level. I hope he keeps going down this path, he has great potential."
Flick handed Espart his debut last season, in March in the Champions League against Newcastle United, and gradually turned to him more, with six further fleeting appearances across the campaign.
The German coach kept a close eye on him from the start - as soon as he got to know him, he compared him to Philipp Lahm.
The real breakthrough came this pre-season, with a string of strong performances.
"He's a top player," Flick said after several friendlies. He was convinced enough to start Espart in both of Barcelona's opening LaLiga fixtures, against Elche and Athletic Club, playing the full 90 minutes in each - despite being deployed on the left, even though his natural positions are right-back and holding midfielder.
Against the Basque side, João Cancelo was fit enough to start but was left on the bench instead, and Espart has also moved ahead of Alejandro Balde in the pecking order.
Espart's calling card is his positional intelligence - he reads the game a beat ahead of most teenagers, and rarely looks rushed even in an unfamiliar defensive role. His passing range and composure recall a deep-lying midfielder more than a full-back, while his recovery pace lets him play higher up the pitch than his frame suggests - the blend behind the Lahm comparisons.
The change of position hasn't stopped Espart showing his attacking side. Against Athletic, he tested Unai Simón in the 59th minute and produced several dangerous crosses, hinting at real quality as a winger or inside forward. He combined well with Anthony Gordon and Raphinha, and picked up a booking for a tactical foul on Iñaki Williams.
His talent has won over Flick and his team-mates alike.
"The defence has been at a great level," goalkeeper Joan García said generally, before adding specifically: "Xavi Espart is incredible."
Pau Cubarsí, another young defender who has showered praise on his versatile team-mate - contracted until June 2028 - added: "We're delighted he's here with us. We grew up together in the academy, with Bernal and Lamine. He's spectacular on the ball, he can play at full-back and in midfield... and he always does it perfectly."
Espart has made eight top-flight appearances so far - five at right-back, two on the left and one in a holding role - but his emergence leaves little doubt: he has arrived to stay, following the path of his successful 2007-born team-mates Lamine Yamal, Marc Bernal and Pau Cubarsí.