Marc-Andre ter Stegen is a doubt for Barcelona's next La Liga meeting with Espanyol, while Arthur will not return in time for the Supercopa de Espana.
Goalkeeper Ter Stegen is undergoing treatment on a tendon problem in his right knee and was declared "unavailable" by Barca on Monday, five days before they return to action against their local rivals.
The Germany international may have picked up the injury in Barca's most recent game, a 4-1 win over Alaves at Camp Nou which sent them two points clear at the top of the table.
While no time frame for Ter Stegen's return to action was provided by the club, they did confirm the Brazilian Arthur will be missing for another three weeks.
The midfielder has been out of action since sustaining a groin injury in the 1-0 victory over Atletico Madrid on December 1, since when Barca have won two and drawn two of their four league games.
Arthur will miss Barca's trip to Saudi Arabia, where they face Atletico in the Supercopa de Espana semi-finals on January 9.
He could return for the visit to Mestalla to face Valencia on January 25.
Barca's Champions League plans should not be affected, as the first leg of their last-16 tie with Gennaro Gattuso's Napoli isn't until February 25.
After a rocky start to the season, things are going reasonably well at Camp Nou.
With another Supercopa within sight, they hold a slender advantage at the top of La Liga and their attacking line seems to be clicking into gear.
Their trio of Lionel Messi, Luis Suarez and Antoine Griezmann all scored in the same game on two occasions in December, with the latter hoping to move past his disappointing early performances.
They may well be active in the January transfer window, with one departure already confirmed.
Carles Alena has left the club to spend the rest of the season on loan at Real Betis , but there is controversy brewing around his fellow midfielder Arturo Vidal.
The Chile international claims he is owed millions in unpaid bonuses , amid rumours he is attempting to force through a transfer to Inter .