While the Indomitable Lions were tamed by Switzerland on Thursday afternoon, their European counterparts suffered at the hands of pundits' favourites Brazil; losing 2-0 to the Selecao despite keeping them at bay for an hour. Both now face an almost win-or-bust scenario in Al Wakrah.
Match preview
Although they managed to hold higher-ranked opponents for the first half of their Group G opener, a 48th-minute goal from Yaounde-born Breel Embolo proved the difference in Cameroon's defeat to Switzerland.
As a result, the West African nation are still seeking their first victory at the World Cup since 2002, when current Cameroonian Football Federation president Samuel Eto'o was the last player to net a winner for his country on the global stage.
After their first-day setback, they have also lost eight World Cup matches in a row, so will now be eager to avoid equalling Mexico's unwanted record of nine in that regard.
Though the Indomitable Lions finished third at last year's Africa Cup of Nations, they have struggled for form ever since; winning just one of their last six outings - and that solitary success came against Burundi.
Rigobert Song's side, who qualified for Qatar in dramatic style by pipping Algeria to the post, arrived in the Middle East as the fourth-lowest ranked team to feature at this year's finals, so are realistic about their prospects.
Dreams of extending their adventure into the knockout stages remain alive, though, and the five-time African champions must at least avoid another loss on Monday. Such a result combined with a draw between Brazil and Switzerland would bring an early end to their campaign; leaving little to play in a final group game against the much-fancied Brazilians.
It was the Selecao who left Serbia pointless after their opening fixture at Lusail Stadium on Thursday, as the two nations reproduced the same result as when they met in Russia four years ago - a 2-0 victory for Brazil.
The repeat was sealed by Richarlison's second-half strikes; handing the Serbians only a third loss in their last 17 internationals. In the aftermath, coach Dragan Stojkovic bemoaned a lack fitness for some of his star players but also acknowledged his team had lost to the better side.
Having crashed out at the group stage in their three previous finals appearances since gaining independence, Serbia have now lost eight of their 10 World Cup matches in total - the most defeats by any European nation.
The Eagles impressed in qualifying, though, and topped their group ahead of Portugal, so will still harbour hopes of turning things around over the coming days and finally reaching the knockout phase.
Indeed, Stojkovic's side also secured promotion to the Nations League's top tier earlier this year, and boasting several proven forwards in their squad, can consider themselves favourites to beat Cameroon and set up a potentially decisive clash with the Swiss on Friday.
Cameroon World Cup form:
L
Cameroon form (all competitions):
W
L
L
D
D
L
Serbia World Cup form:
L
Serbia form (all competitions):
W
D
W
W
W
L
Team News
Despite drawing a blank on Thursday, Bayern Munich forward Eric Maxim Choupo-Moting is likely to keep his place up for Cameroon, given some scintillating form during recent weeks. Rigobert Song could consider turning to his long-serving captain Vincent Aboubakar instead, but the Saudi Arabia-based striker is expected to start on the bench once again.
Whichever centre-forward starts for the Indomitable Lions, Brentford's Bryan Mbeumo will form part of their support act, alongside Karl Toko Ekambi of Lyon. The former made little impact against Switzerland, though, and is still seeking his first international goal.
Meanwhile, midfielder Olivier Ntcham has been ruled out of Cameroon's remaining group games due to injury, so Andre-Frank Zambo Anguissa and Martin Hongla - who both play their club football in Italy - start again in the engine room.
Following his side's defeat to Brazil, Dragan Stojkovic aired his frustration that top scorer Aleksandar Mitrovic and Juventus pair Dusan Vlahovic and Filip Kostic were not fully fit.
While left-winger Kostic is still a doubt, Vlahovic is set to start on Monday and partner Mitrovic up front, with influential captain Dusan Tadic featuring in an advanced midfield role.
Vanja Milinkovic-Savic should hold off the challenges of Marko Dmitrovic and Predrag Rajkovic to line up in goal; joining his older brother, Lazio's Sergej Milinkovic-Savic in the starting XI.
Cameroon possible starting lineup:
Onana; Fai, N'Koulou, Castelletto, Tolo; Anguissa, Ondoua, Hongla; Mbeumo, Choupo-Moting, Toko Ekambi
Serbia possible starting lineup:
V. Milinkovic-Savic; Milenkovic, Veljkovic, Pavlovic; Zivkovic, Gudelj, S. Milinkovic-Savic, Mladenovic; Tadic; Vlahovic, Mitrovic
We say: Cameroon 1-2 Serbia
Serbia have scored freely in recent times, and after being stymied by one of the World Cup favourites in their opening match can now revert to type by finding the net more than once against lesser opposition.