The second-tier rivals have won just 13 out of 45 league games between them this term, but something has to give at the City Ground on Saturday lunchtime.
Forest may be seven points behind Cardiff in the Championship, but they are the side in better form heading into this all-Championship affair.
The Reds beat Preston North End 1-0 last time out and are now unbeaten in five matches, seeing them drag themselves up to 19th in the division.
Cardiff are slightly better off in 15th, but the pressure is continuing to grow on boss Neil Harris following a run of three successive defeats.
The most recent of those losses came away to basement boys Wycombe Wanderers on December 29, with Cardiff's trip to Rotherham last week being called off late on.
The extra four days' rest on Forest may make a difference this weekend, although it is likely that both managers will rotate their sides for this cup clash.
Harris, it should be said, will not be in the dugout for the game after being sent off in that aforementioned defeat to Wycombe.
The former Millwall boss has accepted that he is now fighting for his Cardiff job, with defeat on Saturday potentially being enough for owner Vincent Tan to pull the trigger.
Forest appear to finally be on the way up under Chris Hughton, meanwhile, and they could do with maintaining the momentum they have built with the win over Preston.
Cardiff are not exactly Forest's favourite opponents, though, having lost six in a row against the Bluebirds on home soil - all in the Championship - between May 2015 and September 2020.
That is City's longest winning run away to a single opponent in their history, the most recent of those victories coming four months ago thanks to Kieffer Moore's brace.
Nottingham Forest form (all competitions): LWDDDW
Cardiff City form (all competitions): WLWLLL
Cardiff have a bit of an injury crisis at centre-back as Sean Morrison, Sol Bamba and the recently-recalled Aden Flint are all carrying injuries, while Filip Benkovic has been recalled by Leicester City.
Harris has confirmed that he intends to "mix things up" in terms of his team selection, though the week's rest between matches means that fitness should not be a problem for those not carrying injuries.
As for Forest, Luke Freeman has been building up his fitness and is closing in on a return to first-team action after two months on the sidelines.
Nottingham Forest possible starting lineup:
Smith; Jenkinson, Mbe, McKenna, Bong; Lolley, Yates, Cafu, Knockaert, Mighten; Taylor
Cardiff City possible starting lineup:
Smithies; Bacuna, Cunningham, Nelson, Bennett; Vaulks, Ralls; Ojo, Wilson, Harris; Glatzel
We say: Nottingham Forest 1-2 Cardiff City
Cardiff enter this game on the back of three successive league defeats, while Forest have gone five without defeat, winning two of those.
The Bluebirds have a knack of winning at the City Ground, though, and we can see them picking up a third-round victory on Saturday.