Bayer Leverkusen's fourth victory in five Bundesliga games at the weekend should have put the club in good spirits, but the 3-1 win against VfL Wolfsburg may have come at great cost.
Castro, who can also play as a defender, suffered a pulled hamstring in the closing stages of the Wolfsburg match. He is certain to be unavailable for the Manchester United match.
Hegeler is also said to be doubtful for the Manchester United match too, also due to injury worries. He is to undergo a medical which will determine whether he makes it to Old Trafford.
The fitness of German international Lars Bender is also under review, but the midfielder has travelled with the team.
image: © Paolo Camera