Umtiti, who has grown into an integral member of Ernesto Valverde's first-team at the Nou Camp, suffered a hamstring injury in the 70th minute of Saturday's La Liga clash against Celta Vigo.
Sprinting to keep up with former Liverpool forward Iago Aspas, the France international was forced to pull up, allowing the Celta forward to race through unchallenged and tee up Maxi Gomez to level the contest at 2-2.
Thomas Vermaelen was brought onto replace Umtiti for the final 20 minutes in what was just his second league appearance of the season – with injuries and suspensions seeing the former Arsenal defender drafted in last week against Valencia.
Barcelona have now confirmed Umtiti will miss the next eight weeks – missing the final games of 2017 against Villarreal, Deportivo La Coruna and arch-rivals Real in the final match before the winter break.
"Losing Samuel right now is a big loss, he was in excellent form," Valverde said. "The injury cost us the goal, it was an accumulation of catastrophes, conceding the equaliser and the injury."
Umtiti's injury will also see him miss January games against Levante, Real Sociedad, Real Betis, Alaves and possibly Espanyol.
Barcelona are currently also without centre-half Javier Mascherano who has been sidelined with a hamstring injury of his own since mid-November. The Argentina international is expected to be fit once again for the trip to the Santiago Bernabeu however where he will be expected to come in alongside Pique.
The Argentina international remains absent for Tuesday's final Champions League group match against Sporting CP along with Andres Iniesta, who has been ruled out with a calf injury.
The club captain was replaced after 53 minutes against Celta with the club now confirming he will miss the visit of the Portuguese giants due to "muscle fatigue in his left calf."