Mats Hummels had limped out of Borussia Dortmund's 2-0 win at Wolfsburg with an aggravated Achilles tendon, but is expected to play against Bayern Munich.
Dortmund said that Witsel had activated his release clause -- reported to be around 20 million euros (23 million US dollars).
In a man-of-the-match performance against Hungary in Toulouse on Sunday, Belgium's Eden Hazard turned on the style to score and secure a last eight fight against Wales in Euro 2016.
Belgium's victory was also a welcome return to form by the Red Devils following a disappointing first match in Group E against Italy, which it lost 2-0
