Nagelsmann missed Bayern Munich's 4-0 Champions League win over Benfica on Wednesday due to what the club described as a flu-like infection.
Michael Ballack's authority and versatility saw him become one of the standout players in the German national football team in the early and mid-2000s.
Borussia Monchengladbach beat Borussia Dortmund 1-0 in a Bundesliga fixture at Borussia Park on Saturday.
As per a statement released by the German champions, Sabitzer was given a four-year contract and will wear the No. 18 jersey.
Robert Lewandowski scored his first hat-trick of the season with Jamal Musiala and Thomas Müller also on target in a comfortable win for Bayern Munich against Hertha Berlin.
Before Cristiano Ronaldo returned to Manchester United, we look at five notable players who returned to their former clubs amid great fanfare.
Both Robert Lewandowski and Harry Kane want a transfer - but, as things stand, neither of them seems likely to get one before August 31.
This is the first time Dortmund have lost to Freiburg in Germany's top flight for 11 years, with Saturday's setback coming just four days after losing 3-1 to Bayern Munich in the G...
Dominik Szoboszlai scored with two brilliant strikes while Emil Forsberg and Andre Silva got on the score sheet to complete the drubbing.
Robert Lewandowski scored twice and Thomas Müller added another as Bayern Munich defeated Borussia Dortmund 3-1 to win the Supercup.