The 22-year-old Brazil international, who joined Spartak on a four-year contract from Vasco da Gama in June, tore cruciate ligaments in his knee in a 3-1 win at Rostov.
The defensive halfback will have surgery in Germany, the Muscow club said on their website (www.spartak.com).
Spartak, who host Scottish champions Celtic in the
Champions League Group G match next week, have several key players out
with injuries, including captain Sergei Parshivlyuk and leading striker Welliton.