Ousmane Dembele has been ruled out for five weeks with a hamstring strain to leave Barcelona short of forwards ahead of Sunday's game against Real Betis.
Dembele, 22, underwent tests at the club's training ground on Monday after ending Friday's loss to Athletic Bilbao with a slight problem.
Messi hasn't featured for the club since the end of last season after injuring his calf in his first training session back after a summer break earlier this month.
Suarez, meanwhile, was taking off during the first half of the 1-0 loss at San Mames last week, also with a calf problem.
The Uruguayan is not expected back until after September's international break, although coach Ernesto Valverde could potentially have Messi available for the Betis game this weekend.
Messi has not yet returned to full training with his teammates but has been doing recovery work at the training ground for the last week. Valverde opted not to risk him against Athletic.
Antoine Griezmann, therefore, is currently the only fit first-team forward. Rafinha can also play in a more advanced position, as have the likes of Sergi Roberto and Carles Alena in the past, while B team winger Carles Perez has also been training with the first team all summer.
It leaves Valverde short in attack for the visit of Betis, a game which has grown in importance following a surprise opening day defeat in the Basque Country.
Dembele, a €120 million signing from Borussia Dortmund in 2017, has been plagued by injuries since moving to Camp Nou. He missed the majority of his first campaign at the club with muscle injuries and parts of last season with an ankle injury and a hamstring problem.
His latest in a number of fitness setbacks, coupled with Suarez and Messi both being 32, shows why the Spanish champions are so keen to bring Neymar back to the club.
Sources told ESPN FC on Monday that the club are preparing to make another offer to re-sign the Brazilian this week, firstly on loan with an option to make the move permanent this summer.
Coutinho's move to Bayern -- the ex-Liverpool man was offered in a part-exchange deal last week -- has made it difficult for Barca to sign Neymar outright before the transfer window closes.