The goals have dried up for Sporting Lisbon striker Ricky van Wolfswinkel.
Former Nottingham Forest and Benfica striker Pierre van Hooijdonk says: "He started the season in fantastic form at Sporting, scoring several goals. Everyone was very pleased with the way he was playing, but now he's going through a most difficult time.
"That's part of football. People know he played well at the beginning of the season and must have confidence that he will return to produce good performances again."