Real Madrid and Barcelona put their 100 per cent starts to the Primera Division season on the line at the weekend when they face Athletic Bilbao and Valencia respectively.
For each of the last five seasons, Madrid and Barcelona have occupied first and second place come the end of the 38th game, with Villarreal in 2008 the last side to break up the ages-old near-duopoly.
Valencia, in 2002 and 2004 under Rafael Benitez, and Deportivo La Coruna, in 2000 with Javier Irureta's side, have lifted the league trophy this century, but since those days Barcelona and Madrid have been ever present in the Champions League, usually in its latter stages, and the financial rewards of competing at the top end in Europe has lifted the clubs far ahead of their domestic rivals.
They have the vast squads that can withstand any injury crisis, and the funds available to act in January's transfer window if all is not going to plan.
Barcelona's Lionel Messi and Madrid's Cristiano Ronaldo, by most estimations the world's leading two players, have each played a huge part in their
respective clubs' successes, and barring a seismic event at either another one-two finish looks inevitable.
All of which makes Real Sociedad's home tussle with Atletico Madrid on Sunday an apparent early staging post in the race for third place.
Atletico finished third last term, with Sociedad fourth.
Two games in to the current campaign, and both are unbeaten in the league, with Sociedad also enjoying a smooth path past Lyon in Champions League qualifying this week and Atletico earning plaudits for their efforts in a losing cause against Barcelona in the Super Cup. Following a 1-1 draw in Madrid, Atletico managed a 0-0 stalemate at the Nou Camp, with the trophy going to Barcelona under the away-goals rule.
Atletico have made a flying start to their league campaign, making light of the summer exit of Radamel Falcao in winning at Sevilla and handing a 5-0 thrashing to Rayo Vallecano.
Sociedad have drawn with Elche and beaten Getafe, while also defeating Lyon home and away in Europe.
Atletico can look back on the experience of last season, when for a stretch they held second place before being overhauled by Real Madrid, who in the end finished a hefty nine points clear of their city rivals.
Captain Gabi said after the second leg of the Super Cup on Wednesday night: "We lost the final, that is what counts, but hopefully these two games
will serve us well for the future.
"We have earned the respect of everyone. Barcelona respected us and we managed to stand up to the task. Hopefully we will continue this way."
A similar verdict came from goalkeeper Thibaut Courtois, who said: "The team is still growing. This serves us well for the next game in the league and especially for a match as difficult as we will face in San Sebastian."
Madrid were set to warm up for their Bernabeu clash with Athletic Bilbao by facing Deportivo, now a Segunda Division side, in the Trofeo Teresa Herrera exhibition match in La Coruna on Thursday.
Athletic, like Madrid, have won their opening two league fixtures, beating Real Valladolid and Osasuna.
By Thursday afternoon, Madrid were continuing to await the arrival of Gareth Bale from Tottenham, with the Welshman's anticipated world-record move still incomplete.
Barcelona made their marquee signing at the start of the summer by bringing in Brazil striker Neymar.
He and Messi played together against Atletico on Wednesday, with head coach Gerardo Martino admitting there is work to do to establish their partnership.
"Neymar was also on the left and Leo often does much of his work on the other side, but I have no doubt they will achieve that connection," Martino said.
Valencia, at the Mestalla, will need to pay close attention to the South American pair.
Villarreal, who have followed up their promotion by beating Valladolid and Almeria in their opening two games, travel to Osasuna on Saturday night, when Celta Vigo tackle Granada and Valladolid face Getafe.
Sunday's other games see Espanyol face Real Betis and Malaga travel to Sevilla. On Friday, Almeria play Elche and Rayo Vallecano have home advantage against Levante.