Peter Stoeger starts his colossal task of arresting Borussia Dortmund's freefall down the Bundesliga table on Tuesday while former employers Cologne face a daunting trip to leaders Bayern Munich.

Stoeger has had little time to assess Dortmund's problems ahead of his first match in charge, away to strugglers Mainz.

"In this phase, it's about talking to the boys, finding out about problem areas," said Stoeger, who has signed a contract until the end of the season.

Dortmund are winless in their last eight league games and Stoeger's predecessor Peter Bosz was sacked on Saturday after only 167 days in charge, and following a shock 2-1 home defeat to second-from-bottom Werder Bremen.

That capped a disastrous series of results that saw Dortmund drop from top of the league to eighth.

Stoeger, who described his appointment as a "once in a lifetime" opportunity, is now tasked with rebooting Dortmund's failing season that has also seen them eliminated from the Champions League.

The Austrian, himself sacked by Cologne only a week ago, has had only Monday's training session to prepare for the trip to Mainz, themselves winless in their last three games and just above the relegation places.

Stoeger's immediate concerns are shoring up a leaking defence which has conceded 16 goals in the last six league games, plus coaxing goals from a misfiring attack.

On Wednesday, Bayern, who hold an eight-point lead at the top, will look to pick up a 13th win in their 14 games since Jupp Heynckes took charge.

Germany defender Mats Hummels is struggling with illness, while goalkeeper Sven Ulreich is recovering from a groin strain that saw him miss Saturday's 1-0 win at Eintracht Frankfurt.

Cologne, 12 points from safety, are chasing a first league win this season after the heartbreak of throwing away a three-goal lead in Sunday's 4-3 defeat at home to Freiburg.

Fixtures (all times 1930 GMT unless stated)