The hugely talented Julian Draxler, signed from Schalke 04 for 35 million euros, and Andre Schuerrle, in his first full season at the Wolves, were supposed to plug the gap left by De Bruyne.
Neither was hitting top form regularly, though, and the fans grew antsy as the season looked destined to be a flop, with Wolfsburg managing just one league victory from the end of November until the start of March.
Club officials and coach Dieter Hecking repeatedly had to publicly throw their support behind the pair, saying they needed some time to settle in and the performances would come.
Draxler started delivering last month with two goals in the 3-2 win at Belgium's Gent in the first leg of the Champions League round of 16 tie.
Schuerrle picked up in Tuesday's return leg, scoring a 74th minute winner to send his team to the first ever Champions League quarter-final and hand them their biggest European success to date with a 4-2 aggregate win.
"It is not an everyday occurrence that you reach the last four in the Champions League," a beaming Schuerrle told reporters. "It is something big, something historic for the VfL. It does every one of us a lot of good."
Wolfsburg have rediscovered their winning form at just the right time
They have now won their last two league matches to climb back into seventh place and European contention as well as their last four consecutive Champions League matches.
Despite missing several players through injury, including their top scorer of last season Bas Dost, Hecking's team managed to beat the Belgians twice for a fully deserved last eight spot.
"I am happy that we fought our way through this," said Draxler. "For us it is such a great story because there were some people who did not think we could do much in this competition."
"This will also give us a push in the Bundesliga, where we are not where we would like to be at this stage."
With European heavyweights awaiting in the next round, Wolfsburg are guaranteed a tougher draw than this time around.
"Reaching the last four? Certainly there are some teams where this is going to be very hard," Wolfsburg sports director Klaus Allofs said.
"But there are some others against whom you can have a chance if you play at your very best."
(Editing by Nick Mulvenney)
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