Lionel Messi was absent from Barcelona training on Saturday, with his spot in the squad now in doubt ahead of its announcement.
The Argentina international has been recovering from a calf problem picked up after returning from his summer exploits at the Copa America.
He was absent from Barca's La Liga opener at Athletic Club, which they lost after Luis Suarez went off injured, Aritz Aduriz scoring a sensation overhead kick late on.
As reported by Goal, Messi was absent from training on Saturday, having participated in some sessions during the week, with head coach Ernesto Valverde reiterating that he won't take any risks with his talisman if he isn't fit.
He said: "We won't take any risk with Messi. We must wait to see him in the training session to check if he is ready."
Messi likely wouldn't have started even if he was fit, but the pressure is again on Antoine Griezmann ahead of Sunday's clash with Betis.
The Frenchman looked out of sorts against Athletic, struggling to assert himself in the game following Suarez's exit, who may also be absent from Sunday's clash. Ousmane Dembele is another high profile absentee, having suffered a hamstring problem.
Speaking on Griezmann's start to life at Camp Nou, Valverde added via Marca: "With each passing day, [Griezmann] is integrating better. If he enters the play and participates, he can be decisive.
"At San Mames, he didn't do it as much as we would've liked. We need players who arrive well [in the box]. With the absences we have up front, it is an option that we must take advantage of."
Barcelona are already playing catch up in their defence of the La Liga title, with both Real Madrid and Atletico Madrid winning their opening games. Betis themselves suffered a surprising 2-1 defeat to Real Valladolid on the opening weekend.