Nordi Mukiele, Jocelin Ta Bi and Brian Brobbey all picked up injuries in Sunday's 3-1 home defeat to Fulham, while Le Bris revealed after the game that Romaine Mundle is another concern.
That string of setbacks followed the news earlier this week that Reinildo is facing a month on the sidelines, while Dennis Cickin also missed Sunday's game after picking up what Le Bris described as a "small injury" in training.
Mukiele looked to have injured his calf and Ta Bi - who was making his first start - his ankle, but Le Bris doesn't yet know the severity. The injured players are set to undergo scans on Monday.
"It's a bit early to say, so we had Nordi, Jocelin, Brian, maybe Romain as well, so it was a tough day," said Sunderland's head coach.
"Dennis also missed the game with an injury. At the minute it's a tough period, but it is what it is, we have to accept it and move forward.
"I don't know [the severity] at the minute. It will be clear tomorrow after the scans."
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Sunderland have now lost three games on the spin for the first time this season after Sunday's disappointing defeat.
After a goalless first half lacking in moments of note, Fulham took control with a quickfire double from Raul Jimenez early in the second half.
Enzo Le Fee halved the deficit from the penalty spot before Alex Iwobi secured the points for the visitors late on.
Le Bris bemoaned the "key moments that defined the game", with Mundle missing a glorious chance to open the scoring just before Jimenez's first goal.
Le Bris said: "He was disappointed, like the squad I think and us in general. It is what it is, we have to accept it and move forward."
The head coach added: "A tough day because it's a defeat at home.
"We had the opportunity during the second half to score and just after, they scored twice on set pieces. "Probably our first half wasn't controlled enough, we struggled to find the right rhythm.
"We got two injuries, which didn't help. But we were probably a bit sloppy, lacked quality with the ball and we didn't control this part of the game properly.
"I think the reaction at the beginning of the second half was good, but it was a reaction.
"And after that, just key moments, like in the Premier League. We had a strong opponent, they had the quality to score when it's on.
"We felt the quality in the first half but didn't express it really. So the intention, the lads were positive about their intentions, but we struggled to find the right way to express it."