A shock 1-2 defeat against Japan has meant that Germany have gone from comfortable favourites to qualify for the 2022 FIFA World Cup Round of 16, to now being on the brink of a group stage exit, should they fail to beat a strong-looking Spain team.
An Ilkay Gundogan penalty had put Hansi Flick's team on their way to, seemingly, a comfortable opening fixture. However, a late second-half collapse meant that Japan are now the bookmakers' favourites to qualify from Group E, ahead of Germany.
On the other hand, it was a significantly more enjoyable Wednesday for Spain. They put in one of the most dominant performances in World Cup history, in their 7-0 mauling of Costa Rica. On the night, Luis Enrique's team completed over 1,000 passes and did not concede a single shot at Unai Simon's goal.
The hugely significant goal difference boost leaves Spain top of the group and having a potentially crucial advantage over Germany and Japan - their most likely qualification challengers.
Japan avoiding defeat against Costa Rica and Germany failing to do so, tomorrow, would result in a second consecutive World Cup group stage exit for the European powerhouses.
Even a draw would, most likely, leave Flick's team in a hugely precarious position. In this case, a potential Japan win would give them an unassailable advantage over Germany. In order to qualify, they would have to overcome an eight-goal deficit over Spain, in the last round of fixtures.
With Japan playing before Germany, the situation will be clearer, prior to the evening kick-off.
To summarise, a Japan win tomorrow morning would mean Germany would desperately require to beat Spain. Should Costa Rica be able to get a result, then a draw in the last match of Sunday may not be as bad of an outcome, for the four-time world champions.
Team News
Spain
Enrique should strongly consider naming an unchanged starting 11, given their dominant performance against Costa Rica. The manager had the luxury of making four substitutions, prior to the 65th minute of the match, in order to maintain the freshness of a few of his key players.
Even given Alvaro Morata's impressive substitute cameo - yielding a goal and an assist, it would be difficult to displace any of the Spanish attacking trio; Dani Olmo, Marco Asensio and Ferran Torres all got on the scoresheet, as well.
Rodri was preferred to start alongside Aymeric Laporte, over the more natural centre-back options - Pau Torres and Eric Garcia, in the Costa Rice game. Whether Enrique will opt to select one of that pair may be the only point of contention within the Spain 11, in a game where they will not expect to dominate quite as much as their opener.
There are no apparent injury concerns within the Spain squad.
Germany
Niklas Sule and Nico Schlotterbeck did not cover themselves in glory, during Germany's defeat to Japan. Thilo Kehrer, Lukas Klostermann, Matthias Ginter are among some of the other right and centre-back options within Flick's squad. It would not be a surprise to see one or two of them involved from the start.
Joshua Kimmich's versatility may also come in handy; the Bayern Munich man could move into the right-back spot, to accommodate his team-mate - Leon Goretzka, partnering Gundogan, in midfield.
A quiet performance from Kai Havertz leaves the forward position under question, as well. Nicolas Fullkrug, who replaced Havertz, late in the opening fixture, seems the go-to alternate option. Youngsters Karim Adeyemi and Youssoufa Moukoko are less likely, outside shouts to lead the line.
The availability of Leroy Sane would provide Germany with a huge boost. The winger remained out of action against Japan, but was present in full training, prior to tomorrow's fixture.
Predicted Lineups
Spain
(4-3-3) Simon; Azpilicueta, Rodri, Laporte, Alba; Busquets, Gavi, Pedri; Asensio, Olmo, Torres.
Germany
(4-2-3-1) Neuer; Kimmich, Rudiger, Ginter, Raum; Goretzka, Gundogan; Gnabry, Musiala, Sane; Fullkrug.
Key Players
Spain - Pedri
The 20-year-old midfielder was one of the quartet of players who had the luxury of being withdrawn prior to the 65-minute mark, on Wednesday.
During his 57-minute appearance, Pedri completed 86 passes - averaging just over a pass and a half every minute; this reflects the youngster's crucial role within Spain's team.
He should make up a Barcelona triangle in the middle of the pitch - joined by club teammates - Sergio Busquets and Gavi.
Germany - Leroy Sane
As mentioned, Sane was kept out of his team's opener, due to a knee injury. He seems in contention to return to availability and his selection should be an easy decision to make, for Flick.
Thomas Muller had been fairly anonymous, during the Japan game. Sane's pace would pose a significantly different threat and may be the spark that Germany need to get their campaign back on track.
Match Details
Where is the game being played?
The 68,895 capacity Al Bayt Stadium in Al Khor will host the fixture.
What time is kick-off?
This heavyweight clash will be the main event of the World Cup's Sunday action, rounding off the day's fixtures, at 19:00 BST.
How can I watch?
BBC One will broadcast the fixture, within the U.K.