It appeared that three games in seven days had caught up with Jurgen Klopp's injury-hit side. But Nunez clinched their first win at the City Ground in almost 40 years to leave second placed Manchester City and third placed Arsenal unable to overtake them in the current round of matches.
The Uruguay striker headed home with just seconds left to boost the Reds' bid for a first title since 2020. Quadruple-chasing Liverpool, who won the League Cup last weekend, will hope City slip up against Manchester United on Sunday, with Arsenal facing Sheffield United on Monday.
Defeat was cruel on Forest, who have now won only one of their last seven league games and sit one place above the relegation zone. Divock Origi had Forest fans on the edge of their seats with the game's first shot on goal in the 15th minute as his low 25-yard effort against his former club fizzed past Caoimhin Kelleher's left-hand post.
Liverpool's response was immediate, with the returning Luis Diaz's angled drive being deflected for a corner before Forest should have taken the lead. Origi's precise pass sprang Anthony Elanga clear one-on-one with Kelleher, who saved brilliantly with his legs to deny the Sweden forward.
Forest defender Murillo then thwarted Diaz in front of goal as a high-tempo first half ebbed and flowed. Recalled Forest goalkeeper Mats Selz kept Liverpool at bay at the start of the second period, saving from Andy Robertson, back in action after illness, and Alexis Mac Allister in quick succession.
Liverpool stepped up the pressure but were struggling to carve out chances and Klopp sent on Nunez for his first appearance in four matches after injury along with Wataru Endo. Teenager Bobby Clark made way for Nunez having made his first Premier League
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