The 20-year-old limped off with what looks like an ankle problem and will miss their next Bundesliga match against Union Berlin on Friday, and is unlikely to return before their final game of 2025 against Bayer Leverkusen on December 20.
Nusa had been showing promise this season: he recorded two goals and two assists in 15 appearances.
His absence deepens Leipzig's growing list of injury troubles. Midfielder Assan Ouédraogo is already sidelined with a knee tendon problem ruled to put him out for weeks.
Also unavailable is forward Rômulo Cardoso, who is still struggling with a persistent knee issue.
Despite the setbacks, head coach Ole Werner remains optimistic, stressing that the squad still has the depth and quality to cope: "We are in a situation where we must adapt, but we have players ready to step up," Werner said.
With players like Yan Diomande, Loïs Openda and Benjamin Sesko still fit, and fresh off a dominating win over Frankfurt, Leipzig stay second in the Bundesliga and will be hoping to weather this tough spell without losing ground.