Wolfsburg sporting director Klaus Allofs admits the Bundesliga club have failed to adequately replace Kevin De Bruyne and Ivan Perisic following the duo's departures in 2015.
De Bruyne and Perisic played a key role in Wolfsburg's second-place finish in 2014-15 and their fine performances eventually earned them transfers to Manchester City and Inter respectively.
But Wolfsburg have failed to build on that strong campaign since the exits of two of their key men - finishing eighth last term, while they sit 16th this season - and Allofs has acknowledged selling the two attacking midfielders has cost them.
"We have made a number of decisions in the past that did not prove to be successful," Allofs told Sport Bild.
"It was the right decision to sell De Bruyne and Perisic from a business point of view, even if we knew we would lose a lot of quality.
"On paper, we brought back that quality with the replacements we signed, but these transfers did not pan out as we expected.
"In hindsight, you could say that we have failed to replace De Bruyne and Perisic."