Hummels is one of six Bayern players, including Thomas Mueller, Jerome Boateng and Joshua Kimmich among other, who are part of the squad to face Northern Ireland as they look to seal their World Cup qualification.
World Cup winners Germany, who need one point from their last two qualifiers to secure a spot in next year's tournament in Russia, have won all eight of their Group C games so far. They take on Azerbaijan on Sunday.
German champions Bayern are without a win in their last three matches in all competitions, having dropped to second place, five points off leaders Borussia Dortmund and have twice in a row squandered a two-goal lead in the league.
They sacked Ancelotti and have yet to appoint a successor.
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"We (Bayern players) are in a normal mental and physical state," Hummels told reporters. "We are not new to this business and we have gone through quite a bit in our careers."
"Clearly the past few days or even weeks have not been easy at Bayern, no doubt about that. But why should we be in a different state. We are all fit. Jerome (Boateng) is back after a year so I don't see a problem."
Hummels, whose Bayern were also beaten 3-0 by Paris St Germain -- one of six German club losses in Europe last week -- said the national team was still one of the best.
"It was not a good week for German football and I think it will look better in the coming weeks. But the German national team is at world level."
Northern Ireland, unbeaten in a competitive game at home for four years, are on a five-game winning streak in the group since their only loss of the campaign, a year ago to Germany, and are five points behind them in second place.
"I don't think the Bayern players are feeling any effects from the situation in Munich," Germany coach Joachim Loew told reporters. "I detect no nervousness nor tension."
"They know how to deal with the situation. It is not the first time they have been through a club crisis."
(Reporting by Karolos Grohmann; Editing by Keith Weir)
