Manchester United manager Jose Mourinho has likened Romelu Lukaku's current goal drought to shaking a ketchup bottle as the striker prepares to face his former club Everton.
Lukaku has often gone through barren spells in front of goal during his playing career, followed by ruthless scoring streaks which have resulted in him having an impressive goals-per-game ratio of 0.45 in the Premier League.
Speaking in an exclusive interview with Sky Sports ahead of United's Super Sunday clash against Everton, Mourinho says he expects Lukaku's next purple patch to not be too far away.
Live Renault Super Sunday
He said: "I think one of the best scorers in football had funny words about it. It was when Cristiano Ronaldo was speaking about the ketchup bottle and when you [shake it]. The goals are coming and coming and coming.
"I believe with Lukaku that this will happen, but the reality is that in this moment it's not happening.
"There's been lots of matches in which he's not scored a goal, and not just scoring but also the performances, the happiness in the performances, I think is the problem.
"But he's a good player, a good boy, and I think the best way to do it is to just keep working and the moment will arrive."
Mourinho is wary of the threat Everton pose his side this weekend, with the visitors having already scored six headed goals this season in the Premier League - more than any other team.
Conversely, United have struggled to defend set pieces, and Silva will look to exploit United's weakness at Old Trafford.
Mourinho missed out on signing Yerry Mina from Barcelona during the summer, with the Colombia international yet to make his Everton debut following a prolonged period out injured.
Mina is expected to have to settle for a place on the substitutes' bench given the form of Kurt Zouma and Michael Keane, and Mourinho says this weekend's opponents have been able to invest without the same level of pressure to succeed.
"Everton have one advantage in relation to us, which is a similar potential, but much less expectations," Mourinho added.
"Everything they do nicely is positive, the mood has been calm during their investments.
"They've improved their team, they've had time to work, no pressure at all, and the potential is very similar.
"We have on us that extra factor that we are Manchester United, but we have to be strong enough and brave enough to know that it's a game that we can win."