Steve Cooper's men were torn apart with Alex Iwobi and Raul Jimenez both netting two goals each before Tom Cairney completed the rout.
Former Chelsea and West Ham defender Scott Minto was in attendance for talkSPORT, and couldn't believe what he was seeing at the City Ground.
Responding to the fifth goal, Minto said: "I said it was embarrassing at 4-0, I don't know what's worse than embarrassing to be honest with you.
"The Forest fans, they should get their money back for what they've seen here, it's not been good enough.
"Just when you're wanting some kind of performance… You can lose at the Cottage but this is absolutely disgraceful, they've absolutely capitulated, given the ball away.
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"Fulham have been superb, I've got to give them credit for being so clinical, but I do worry for Forest and Steve Cooper now if the rumours [of him being sacked] are true."
The result means Forest fall to 16th in the Premier League table. They are currently six points clear of the relegation zone.
It will also throw up further questions about the Welshman's future. talkSPORT understands Crystal Palace will make an approach for Cooper should he leave the City Ground.
Breaking news. More to follow.
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