The 19-year-old had completed the full 90 minutes for La Roja in their 3-1 win over Cyprus on Friday, and Luis de la Fuente kept him in the first XI for the visit of Georgia to Valladolid in their final Group A fixture.
However, with 26 minutes on the clock, Gavi jarred his knee while attempting to control a long ball and grimaced in pain as he hobbled across the field, eventually being replaced by Oihan Sancet.
There were immediate fears that the teenager had sustained a potentially season-ending injury, and Barcelona have now confirmed the worst, revealing that Gavi's ACL has torn completely.
In addition, the former Kopa Trophy winner has also suffered an associated injury to his lateral meniscus, and an operation is scheduled for the coming days, after which a new update will be released.
"Test carried out on Monday morning on the first team player Gavi have shown that he has a complete tear of the anterior cruciate ligament in his right knee and an associated injury to the lateral meniscus," Barcelona said in a statement. "The player will have surgery in the coming days after which a new medical update will be released."
The La Liga champions also offered supporters the chance to share a message of support for the youngster on their website, adding: "The Andalusian midfielder is a firm favourite amongst the fans.
"Gavi's spirit and determination on the field are what defines him as a player and he gives absolutely everything in a Barca shirt. For that reason his injury is a big blow for all Barca fans."
While Barcelona did not speculate about the length of Gavi's absence, the Spain international is expected to spend at least seven and possibly as many as nine months in the treatment room, ruling him out of the rest of the domestic season.
Spain are also fearful that they will not be able to call upon the Barcelona man for Euro 2024, which they had already qualified for prior to Sunday's showdown with Georgia, where Robin Le Normand, Pau Torres and a Luka Lochoshvili own goal gave La Roja a 3-1 win.
La Blaugrana were apparently left enraged at the Spanish Football Federation for risking Gavi in a largely inconsequential fixture, and Mundo Deportivo reports that the club could now receive up to €5m (£4.4m) in compensation.
After bursting onto the scene in the 2021-22 season, Gavi has continued to play an important role in Xavi's system this term, scoring two goals and setting up one more in 15 appearances in all competitions.
The La Masia graduate - who has been with Barcelona since 2015 - has already made 111 appearances for the Catalan giants in all tournaments, registering seven goals and 14 assists in the process and winning the 2022 Kopa Trophy and Golden Boy awards.
Gavi is one of two fresh injury concerns to emerge for Barcelona during the international break, as first-choice goalkeeper Marc-Andre ter Stegen withdrew from the Germany squad due to a back problem.
Frenkie de Jong (ankle) and Sergi Roberto (calf) have also been in the care of the Barcelona doctors ahead of the resumption of domestic football, which sees Xavi's side travel to Rayo Vallecano on Saturday lunchtime, although the duo and Ter Stegen are believed to be winning their battles to be fit for that match.