Borussia Dortmund boss Thomas Tuchel has hailed the impact of returning forward Marco Reus.
Reus missed the first three months of the season due to an adductor injury, but returned with a bang in Dortmund's record-breaking 8-4 win over Legia Warsaw in the Champions League on November 22.
The Germany international has had a hand in nine goals in just four games this term, including a late equaliser at Real Madrid in midweek, and Tuchel recognises how important he is to Dortmund's hopes of claiming some silverware this season.
"His achievements are remarkable," he told a news conference ahead of sixth-placed Dortmund's trip to Cologne on Saturday.
"I was worried when Marco missed the Euros. Then we saw how professional, patient and determined he was as he worked toward his comeback.
"He has always had great self-confidence, he knows his quality.
"He fills a vacuum, that is the greatest complement I can pay him.
"He is a great reference point for the young players here."
Dortmund's comeback from 2-0 down in Madrid on Wednesday meant they topped Champions League Group F but their excellence in Europe has not always been matched domestically this season and they go into the weekend nine points behind surprise leaders RB Leipzig.
A trip to a Cologne side one place and two points behind them in the Bundesliga is another tricky assignment, as Tuchel acknowledged.
"We want to take points, ideally all three," he added.
"But they have continuity, quality, calmness and have done some very good transfers.
"It is always unpleasant to go there, it is a very emotional place and we have to fight against that."
Tuchel, who conceded the squad had had very little time to train after returning from Spain, will be without Mario Gotze this weekend as he is suffering from knee pain but Marcel Schmelzer and Sokratis Papastathopoulos are expected to be fit.