A clash of heads with Nurnberg's Tomas Pekhart in the first half of Saturday's 2-2 draw has brought an end to the midfielder's season.
"It was a shock and it still is a shock," said Freiburg coach Christian Streich after the game.
Schuster was diagnosed with a broken nose and upper jaw and he underwent surgery in Freiburg on Monday.
He will therefore have to watch on as his team-mates try to avoid relegation to the second division without him, and a win in the capital on Tuesday would be a huge step towards that goal.
The two clubs are currently separated by five points with Hertha coach Otto Rehhagel, whose side are second from bottom, aware that Tuesday's game could be his side's last chance.
However, he feels his players now fully understand the severity of the situation.
"My team has finally accepted the relegation battle," he said after a draw with Borussia Monchengladbach on Saturday.
"This makes me confident for the Freiburg game."
Freiburg's director of sport Dirk Dufner strangely believes relegation would not be a tragedy for his side.
"If things were to go wrong this year, then it would not be the end of the world," he told Sport1 television.
"But we do need to think more about the first division than the second, but if it really were to be (relegation), then we would be able to lift ourselves up again."
Dufner has particular belief in Streich.
"Christian Streich is one of the best coaches in Germany for bringing through young players," added Dufner.
"We knew what we were going to get with him. The only problem was appointing him as head coach meant removing the whole lower structure of the club and that is why we initially appointed Christian Sorg.
"The decision to then appoint Streich was not purely to stay in the Bundesliga, but to think in terms of the future.
"He turned us down to start with, but in the end, he accepted."