Borussia Dortmund has a new coach and hopes that a flurry of new signings will help turnaround an underwhelming season so far.

Niko Kovač started work as coach on Sunday, taking over from unbeaten interim coach Mike Tullberg, who stepped up from the club’s under-19s for three games after Nuri Sahin was fired. Sahin, a club favorite from his playing days, was let go as coach after starting the year with four defeats.

Meanwhile, Dortmund was working on transfers on Monday, the last day of the winter transfer window. The club said Swedish defender Daniel Svensson was joining on loan from FC Nordsjælland with an option to buy. Chelsea winger Carney Chukwuemeka and Ajax goalkeeper Diant Ramaj are expected to join.

But the club's move to sign Lyon midfielder Rayan Cherki appeared to collapse with American businessman John Textor, the owner of Lyon, turning down a reported offer of 22.5 million euros ($23.2 million) for the 21-year-old player.

Kovač will have little time to work with any new arrivals before a crunch Bundesliga clash with Stuttgart on Saturday. Stuttgart, last season’s runner up, lost its last three games across all competitions and is bidding to stop that run against Augsburg in the German Cup quarterfinals on Tuesday.

Dortmund has already been knocked out of that competition by Wolfsburg, one of Kovac’s former clubs.

The Berlin-born former Croatia midfielder’s biggest successes as coach came first in charge of Eintracht Frankfurt, which he led to a German Cup final win over Bayern Munich in 2018. He then led Bayern to a league and cup double the following season.

Dortmund presents a formidable challenge with problems beyond the field amid reports of disharmony between managing director for sport Lars Ricken, sporting director Sebastian Kehl and team planner Sven Mislintat. Chief executive Hans-Joachim “Aki” Watzke is stepping down at the end of this year.

The inexperienced Sahin, who was coach Edin Terzić’s assistant last season, should arguably not have been given the role of head coach. But he’s not the first to falter. Kovač is the ninth coach to take charge of Dortmund since Jürgen Klopp stood down in 2015.

Kovač has been tasked with leading Dortmund to a top four finish in the Bundesliga for Champions League qualification. The team is currently 11th in the 18-team division, four points behind fourth-place Leipzig after 20 rounds.

After Stuttgart on Saturday, Dortmund faces Sporting Lisbon away in the Champions League playoffs on Feb. 11 with the return game at home on Feb. 19.

Kovač will need to tighten a defense that has been prone to blackouts and comedy-reel mistakes. Goalkeeper Gregor Kobel gifted Shakhtar Donetsk a goal in the Champions League last week.

Defender Waldemar Anton has looked a shadow of the player he was at Stuttgart last season. Up front, Serhou Guirassy has struggled since joining from Stuttgart, where he starred with 28 goals in 28 Bundesliga games last season.

Kovač will be able to ask Stuttgart coach Sebastian Hoeneß how to get the best out of the players when they meet again in the Bundesliga on Saturday.

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