Marcelo Bielsa says Leeds must urgently rediscover their cutting edge if they are to have any chance of returning to the Premier League for the first time since 2004.
The Championship side have squandered an 11-point cushion in the race for automatic promotion.
Leeds remain second in the table, four points behind leaders West Brom, despite Saturday's 2-0 defeat at Nottingham Forest, but have lost five of their past 10 league matches ahead of Tuesday's crucial trip to promotion rivals Brentford.
Bielsa believes the reason for Leeds' slump is their lack of confidence and form in front of goal.
Since a 5-4 win at Birmingham on December 29, Leeds have scored just four goals in seven games in all competitions.
"There are good things the players are doing on the pitch and also mistakes," Bielsa said on Monday.
"Before maybe we didn't pay consequences for the mistakes in the good moments, but now we are paying higher consequences.
"We used to create chances and score those chances in the good moments of the team and now we have those chances and we are not scoring."