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."
Leeds were 11 points clear of third place after securing a seventh successive league win by beating Hull in early December.
But the defeat at Forest, now in fourth place, left them level on 55 points with third-placed Fulham and only two ahead of Tuesday's opponents Brentford.
The losing run shaken the faith of some Leeds fans after they squandered a good position in last season's promotion hunt.
Yet former Argentina coach Bielsa is sure his players' confidence remains unaffected.
"It's just about scoring the chances," he said.
"The positive things the team used to do, we used to transform into good things and now we are not doing that.
"The team is not playing worse than before. The team is not running less, it's running even more and the team keeps the same confidence of before.
"It's not useful to give more explanations because the results speak for themselves and the results are bad.
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