Second-placed Atletico will play after third-placed Real Madrid but before leaders Barcelona on Saturday, and any slip could see Diego Simeone's side out of the running with just two games left.
Atletico boss Simeone is so often the driving force from the touchline when the going gets tough for his team, but the Argentine will not be allowed to influence matters for the rest of the season as he starts a three-game ban.
Simeone paid the price for an incident during his team's 1-0 win over Malaga last weekend, when a ball was thrown from Atletico's technical area onto the field while the visitors were on a counter-attack.
The 46-year-old's team have won their last five league matches though. and that run of form has seen them occupy second position in the table with just three games to play. Leaders Barcelona are only ahead of Atletico on the head-to-head record, while Real Madrid sit one point behind in third.
On Saturday afternoon, Real Madrid will travel to Real Sociedad, before Barcelona play the late game away to Real Betis. In all likelihood, Atletico will end the night in second spot once again and they will have to rely on Barcelona to slip in their final three games in order to win the title once again.
Atletico, meanwhile, will travel to Levante next weekend, before hosting Celta Vigo on the final day of the season. Simeone's side also have a Champions League semi-final second leg to think about, however, as they prepare to travel to Germany next week protecting a 1-0 lead from the reverse match in Madrid on Wednesday night.
Atletico have now kept 22 clean sheets in La Liga this season, which represents their best total, while they have only shipped 16 goals in their 35 league matches. They have only hit 59 goals in comparison to Real Madrid's 104 and Barcelona's 102, but they have once again been sensational at the back.
Not since September have Atletico lost a league match on home soil and that was a 2-1 reverse to Barcelona. In March, Barcelona managed to open up an 11-point lead at the summit, but Atletico have eaten away at that total and are very much in the running as a pulsating La Liga season draws to a close.
Recent form: LWWWWW
Recent form (all competitions): WWWWWW
At this stage of the season, there are a number of clubs in La Liga simply going through the motions. Rayo are not one of them, however, which makes them dangerous opponents for Atletico this weekend.
The home side need all the points to keep their title challenge alive, but Rayo are currently 17th in Spain's top flight and just two points outside of the relegation zone with three games left.
Not even basement side Levante have been cut adrift and just six points separate Rayo from the bottom of the table. Taking something from this weekend's match is a very big ask, but Paco Jemez's side have a massive game away at Real Sociedad next Sunday, before hosting Levante on the final weekend of the season.
Eight wins, 11 draws and 16 defeats have left Rayo fighting the drop, but they have scored 48 times in their 35 league games, which is the best record in the bottom half of the table. They have conceded 69 times, however, which is the poorest defensive record in the whole division.
The capital side led 2-0 at home to Real Madrid last weekend, but ultimately lost 3-2 as Los Blancos recorded a ninth straight league success. Jemez's side have actually only lost two of their last seven in Spain's top flight, but they will enter week 36 fighting for their lives at the bottom.
Rayo are currently in their fifth successive La Liga campaign and have not finished lower than 12th in the last three seasons. Their destiny is still in their own hands, but they have work to do to avoid sliding into the Segunda Division.
Recent form: DWLWDL
Atletico possible starting lineup:
Oblak; Juanfran, Lucas, Gimenez, Luis; Gabi, Koke, Augusto; Griezmann, Vietto, Saul
Rayo possible starting lineup:
Carlos; Tito, Crespo, Amaya, Quini; Iturra, Jozabed; Bebe, Hernandez, Adri; Guerra
Head To Head
Atletico have lost just one of their last 12 La Liga matches with Rayo and have won each of their last five meetings at the Vicente Calderon, which is their best ever run against their neighbours.
Earlier this season, Atletico recorded a 2-0 win in the reverse league match, while Simeone's side also knocked Rayo out of the Copa del Rey this season courtesy of a 4-1 aggregate score.
What's more, Atletico are unbeaten in their last 17 Madrid derbies - recording 14 wins in the process.
We say: Atletico 2-0 Rayo
Rayo are still battling for their lives, but Atletico need all the points to remain in the title hunt. It is possible that the home side will have a European hangover, but they should still have more than enough to triumph.