Kobel is out with an injured ligament and Witsel has an infection.
Second-placed Dortmund are already missing Mats Hummels, Donyell Malen, Mahmoud Dahoud, Thomas Meunier, Thorgan Hazard and Giovanni Reyna.
A home win would leave Bayern an unassailable 12 points ahead of second-placed Dortmund with three games left.
Despite their lengthy casualty list, Dortmund intend to deny the hosts securing a tenth straight Bundesliga crown.
“We want to try to prevent that. That’s the task, that’s the goal,” said Dortmund coach Marco Rose.
The German media refers to Bayern-Dortmund matches as ‘Der Klassiker’ (The Classic).
Yet Bayern are chasing an eighth straight win in the series, having scored 30 goals, conceding just five.
Dortmund have winger Raphael Guerreiro back from injury.
They hope to collectively slam the brakes on Bayern’s attack, spearheaded by former Dortmund striker Robert Lewandowski who has chalked up 32 goals in the Bundesliga alone this season.
“We have to defend against their attacking power and create our own chances,” said Rose.
Meanwhile in Munich, most of the Bayern squad is fit with a sell-out crowd of 75,000 expected.
There is a question mark over winger Kingsley Coman, who is carrying an ankle knock, while defender Niklas Suele is fit and set to face future employers Dortmund, who he joins next season.
Bayern’s Champions League exit to Villarreal in the quarter-finals last week remains a sore point. “The last two weeks are clouding the mood,” admitted head coach Julian Nagelsmann.
Nevertheless, Bayern are already anticipating a win and planning a party, which traditionally involves Bayern stars dousing each other with enormous glasses of beer.
“I’m open to everything, even a beer shower,” quipped Nagelsmann.
“I once read that a beer cure is quite good for the hair…”