Bayern Munich sporting director Christoph Freund guaranteed coach Thomas Tuchel would be in the dugout for Tuesday's Champions League game at Arsenal despite Saturday's 3-2 loss to Heidenheim.

Bayern had a two-goal lead at half-time but conceded three goals to the promoted club, which left Xabi Alonso's Bayer Leverkusen -- who won 1-0 at Union Berlin -- on the cusp of a first Bundesliga title.

Leverkusen are 16 points clear and need just one win from their remaining six games to lift the title, with Bayern having won the previous 11 league crowns.

Freund told reporters Tuchel would "100 percent" be in charge for the quarter-final first leg in London, despite admitting "losing twice in a week is incredible".

"In three days we've got a very important match. Thomas was trying to bring back energy, to see what things need to be changed and what isn't working," he said.

Tuchel won the Champions League as Chelsea coach in 2021, having taken Paris Saint-Germain to the final the year before, when they lost to Bayern.

Bayern lost at home to Borussia Dortmund last Saturday, the visitors' first win in Munich since 2014.

Freund also reserved some harsh criticism for Bayern's players, saying giving up the lead was "unacceptable".

"Every player must look in the mirror after the match and ask themselves if they gave everything for the team," he added.

"We cannot concede three goals in the second half after leading 2-0 at the break.

"We need to ask ourselves questions as a group. This is not acceptable."

Heidenheim coach Frank Schmidt, who has been in charge for over 16 years and taken the club to the top flight from the fifth tier of German football, implied Bayern were complacent.

"A lot of teams come here and think about how big the win will be. But we took risks and attacked the goal in the second half."