Wolfsburg's coach Dieter Hecking cracked the whip on Sunday with his team in Bundesliga free-fall since knocking Manchester United out of Europe and their Champions League clash at Ghent just 10 days away.

Wolfsburg booked their place in the Champions League's last 16 as group winners with an impressive 3-2 home win over United on December 8 as Germany midfielder Julian Draxler ran Louis van Gaal's Red Devils ragged and Brazil defender Naldo netted two headers.

The victory consigned United to the Europa League while Wolfsburg reached the Champions League's knock-out stages for the first time in the club's history.

But league results have taken a downward spiral since with Wolfsburg winless in their last five games and Saturday's lifeless 3-0 defeat at Schalke in Germany's top flight snapped Hecking's patience.

Instead of the usual gentle recovery session, the Wolfsburg squad found themselves sweating during an intense 100-minute session on Sunday morning.

Ghent, who are top of the Belgian league, host Wolfsburg on February 17 with the return leg in Germany on March 8 and Hecking has much to sort out if his club are to reach the quarter-finals in Europe

"I'm annoyed and with good reason," fumed Hecking.

"If Schalke had counter-attacked us better before the half-time break, then it could have been three or four-nil (at half-time).

"That's very alarming. In the second half, it was just about damage limitation.

"It's not enough. The team is not playing like a team at the moment. That is the basic problem."

Having been fourth in mid-December, the alarm bells started ringing after a shock 3-1 defeat just before Christmas at Stuttgart, who left the relegation places as a consequence, sent Wolfsburg tumbling down to seventh.

Then came a 3-2 loss on their January return after the winter break at Eintracht Frankfurt, whose captain Alexander Meier hit a hat-trick, followed by a 1-1 draw at Cologne last weekend before the crash to Schalke left them eighth.

Wolfsburg were 2-0 down at the break at Schalke as striker Klaas-Jan Huntelaar netted his first league goal for two months before midfielder Johannes Geis drilled in a free-kick.

Then new-signing Alessandro Schoepf netted a late third for Schalke as Wolfsburg failed to take their chances despite dominating possession.

Draxler had to deal with jeers, boos and whistles from the home fans on his first return to Gelsenkirchen since signing for Wolfsburg last August for 35 million euros ($39 million), after 14 years with Schalke, following Kevin de Bruyne's sale to Manchester City.

"It was nice to see a few old faces again, but in general it was a game to forget," said the 22-year-old Draxler.

"I can understand the fans, but we lost an important game 3-0 and that's bitter."

The Wolfsburg squad can expect more tough sessions ahead of next Saturday's home league match against mid-table Ingolstadt before they take on Ghent.

"Right now, there are no positives to take, but I know which wheels I have to set in motion," said Hecking.

Wolfsburg's director of sport Klaus Allofs says his coach's position is not under threat - for now.

"For me, the coach's position doesn't come into question," added Allofs.