Athletic Bilbao against Real Madrid is one of the classic La Liga fixtures.
One of the earliest fixtures from the very beginnings of the league, the Basques against the establishment, for want of a better description, will also hold cachet for the Spanish top flight connoisseur.
It's also a fixture that Los Blancos enjoy, almost always coming out on top against Los Leones.
This season, more than any other in recent memory, the lions need to come and fight, not only to preserve their own La Liga status of never having been relegated, but to ensure that this season has been a moderately successful one for Ernesto Valverde.
Let's take a look at three things that will shape the outcome of this one.
Ronaldo to hit top form again
It's been a long time coming. Not until last weekend did we see the first La Liga goal in open play from a player that looked like, pre Christmas, that he would break every scoring record available.
At least there can be no complaints from the Bernabeu faithful that Ronaldo hasn't been trying.
He's done everything but score just recently and the frustration is clear for all to see.
What more incentive does he need to rediscover his top form than nemesis Lionel Messi coming right up on the rails in the race to the Pichichi title.
There was a time not so long ago that the Argentine laboured 13 goals behind his contemporary. Now the gap is just two.
This is the perfect game for the Portuguese to find his shooting boots again.
History against the Basques
Not too many sides have the opportunity of defeating Real Madrid on a regular basis, but few can have as bad a record as Athletic Club.
Over the course of the last ten years, Los Leones have triumphed just twice - in 2005 and 2010. In the same space of time, Real have won an astonishing 19 fixtures between the pair, often by four goals or more.
They've yet to conquer the New San Mames but that is only a small crumb of comfort to the home support, still reeling from the five-star showing of FC Barcelona just a few weeks ago.
Laporte and Varane - two of the best
The attackers of any club almost always get the plaudits but it's worth taking time out to acknowledge the excellence of these two young talents.
At just 20 years of age, Aymeric Laporte has already had a £36 million buyout clause on his head for well over a year.
It's perhaps with that in mind that he hasn't yet moved on to a bigger club.
Although there is little doubt this accomplished exponent is worth every penny, it remains a major investment for one so young.
At the opposite end of the field, Varane is looking every inch a future Real Madrid captain.
After a dip in form and confidence, the young Frenchman has rediscovered his touch and composure and is now rivalling Sergio Ramos and Pepe as first choice at the back for Los Blancos.
Expect both to have a big say in where the points end up this Sunday.
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