DORTMUND, Germany — Borussia Dortmund sacked Peter Bosz as coach after managing just one win in 13 games across all competitions and named former Cologne coach Peter Stoeger as his replacement on Sunday.

Stoeger was sacked as Cologne coach the previous Sunday after his side failed to win any of its opening 14 Bundesliga games of the season.

The club said the 51-year-old Stoeger and his assistant coach Manfred Schmidt, who was also let go by Cologne, were signed until June 30, 2018.

Stoeger, who joined Cologne in 2013 and led it to promotion from the second division in his first season, said it was a "surprising situation" to be called Saturday night by Dortmund, "but also an extraordinary chance for me."

Stoeger oversaw steady progress at Cologne, culminating in fifth place and Europa League qualification last season. But this season didn't go to plan.

Bosz's last game in charge of Dortmund was Saturday's 2-1 defeat at home to relegation-threatened Werder Bremen, a loss that stretched the side's winless run to eight games in the league.

"We decided yesterday evening in a talk with Peter Bosz that we're letting him go with immediate effect," Dortmund chief executive Hans-Joachim Watzke said. "It was emotional."

Dortmund previously had a 41-game unbeaten run at home, but since Leipzig inflicted a 3-2 loss on Oct. 14, the side slumped to two defeats and a draw at the Westfalenstadion. The draw came after squandering a four-goal lead to allow bitter rival Schalke to draw 4-4.

Bosz led Dortmund to its best-ever start in the Bundesliga with six wins and a draw from seven games and a league-high goal difference of 19. It led the league by five points after beating Augsburg 2-1 away on Sept. 30 but hasn't won since.

Now the side trails Bayern Munich by 13 points, a turnaround of 18 in just eight rounds.

Dortmund next faces a trip to Mainz in the Bundesliga on Tuesday.

"We're training today at 3 p.m. There's another training session tomorrow, then we'll make our way to the opponent," Stoeger said. "For now it's about empathy and getting to know the team and the staff."

Sunday's training session was forced indoors, however, due to heavy snow.

Bosz, who led Ajax Amsterdam to the Europa League final and second place in the Dutch league last season, was hired in June as a replacement for Thomas Tuchel, sacked the week before despite winning the German Cup after falling out with club management.

Watzke and sporting director Michael Zorc were keen on Bosz's style of attacking football, continuing a mould started by Juergen Klopp, who won two successive Bundesliga titles, before it was refined under Tuchel, who took over in 2015.

The 54-year-old Bosz, a fluent German-speaker, signed a two-year contract with Dortmund. Watzke said at the time the club assumed it would be longer.

"Unfortunately we all failed to achieve the desired results to the circumstances. I am so sorry about that," Bosz was quoted as saying on Dortmund's website, where he thanked the club, the team and the fans.

"For the future, I wish the best for the club and will keep my fingers crossed," Bosz said.