Nuno Espirito Santo spoke about Forest's final five games of the season being the "biggest of our careers" in the build-up to this encounter, but that wasn't enough to draw a reaction from his troops.
Following a disappointing showing on the big stage at Wembley against Manchester City, it was imperative that Forest quickly got back on the horse in the league with the Champions League in their sights.
However, much like the FA Cup semi-final, Forest lacked in all areas as Brentford found life far too easy at a ground that has been a fortress for most of 2024-25.
Elliot Anderson registered Forest's only shot on target in the first half but it was a routine save for Flekken.
Nuno opted to shake things up at the break with Nicolas Dominguez brought on for Callum Hudson-Odoi and it initially appeared to be the right call as Forest started brightly.
Elanga, despite being isolated, managed to carve out a sight at goal after driving into the box and his shot was destined for the bottom corner until Flekken tipped it away for a corner.
Wood, who is only one goal shy of becoming the second Forest player to hit 20 in a Premier League season after Stan Collymore (22), struggled to impose himself on the game.
With four games left to play and at least five spaces up for grabs in the Champions League, Forest still remain firmly in the hunt, but defeat - a third in four league outings - means they have lost some control of their destiny and need to rely on others to drop points.