The visitors have gone four games without a win but are still well placed to finish in the top six, while Barnsley lost again in midweek and are heading back to League One.
Barnsley's performance against table-topping Leeds United on Thursday belied their position at the foot of the division, but they had nothing to show for it in the 1-0 defeat.
That was ultimately down to their inability to put the ball in the net, which boss Gerhard Struber admitted has been a major problem for his side this term.
Only Middlesbrough have scored fewer goals than Barnsley in 2019-20 and the Tykes now face the prospect of being relegated even if they beat Forest and Brentford.
Struber's side are four points adrift of 21st-placed Charlton Athletic, who play Wigan Athletic and champions-elect Leeds United in their remaining two matches.
All Barnsley can do is pick up three points this weekend and hope that other results on Saturday go their way, ensuring that their relegation battle will go down to the wire.
Realistically speaking, however, two defeats and two draws in their last four matches has not been enough and their one-year stay in the second tier is coming to an early end.
There may be a two-division gap between these teams next term should Forest achieve their aim of promotion.
The first step is to secure a top-six finish, which they can do with a maximum of two points from games against Barnsley and Stoke City over the coming days.
Seventh-placed Millwall have a five-point deficit to make up on the Reds and face Queens Park Rangers and Huddersfield Town in their last two fixtures.
Sabri Lamouchi will perhaps be a little concerned by his side's form heading into the playoffs, though, given that they have drawn three and lost one of their last four matches.
The 2-2 draw with Swansea City last time out may have showed Forest's fighting spirit to twice hit back, but they need to step things up again if they are to rebuild some momentum.
Barnsley's Championship form: DWLDDL
Nottingham Forest's Championship form: WWDLDD
Barnsley used a three-man defence against Leeds but may opt to go with four-at-the-back on Sunday, which could see Aapo Halme dropping into the backline.
Romal Palmer remains the hosts' only injury absentee, having missed the last four matches with a knee injury that will keep him out until next season.
One player certain to start is Conor Chaplin, who has been directly involved in eight of Barnsley's last 14 league goals at Oakwell, scoring seven and assisting one.
Striker Lewis Grabban has scored just one goal in his last five outings but is favourite to lead the line for Lamouchi's side.
Barnsley possible starting lineup:
Sahin-Radlinger; Sollbauer, Andersen, Halme; Ludewig, Styles, Mowatt, Ritzmaier; Woodrow; Brown, Chaplin
Nottingham Forest possible starting lineup:
Samba; Jenkinson, Figueiredo, Worrall, Ribeiro; Sow, Watson; Lolley, Silva, Ameobi; Grabban
We say: Barnsley 0-2 Nottingham Forest
Barnsley have kept three successive clean sheets at Oakwell, but Forest have netted 10 times across their last four visits to this ground. The visitors will be looking to return to winning ways in order to seal a playoff spot and we are backing them to do exactly that on Sunday, officially relegating their opponents in the process.