Ronald Koeman backed Antoine Griezmann but said goals would be the "best medicine" to boost the Barcelona forward's confidence.
Griezmann's last goal came against Ferencvaros in the Champions League on December 2, and he has just three in 16 LaLiga appearances this season.
A trip to Los Carmenes to face Granada on Saturday could help the France international, who has been involved in four goals (three goals and one assist) in his past five visits to the ground in LaLiga.
Barcelona coach Koeman said while Griezmann was working hard, goals would be best for the 29-year-old.
"Any player needs confidence in himself, his team-mates and the place where he plays. This starts with the player," he told a news conference.
"As a coach, I can communicate with [Griezmann], show him things and footage of potential things to improve, but at the end it's the player who has to show his quality and give effectivity to the team.
"It's not the case that Antoine doesn't work, he works a lot in any position. The other day he recovered a lot of balls, he gave an assist to Leo [Messi].
"But it's time that he scores, because scoring goals is the best medicine to have total confidence in yourself."
Griezmann has converted just 22.2 per cent of his big chances in LaLiga this season, his lowest in any campaign since at least 2012-13.
Barcelona are fourth in the table, seven points behind Atletico Madrid but having played two more games.