(CNN)It is arguably sport's most intriguing two-horse race.
Spain's La Liga kicks off this weekend and all eyes will be on Real Madrid and Barcelona and their respective star players -- Cristiano Ronaldo and Lionel Messi.
Over the last 10 years, those two clubs have shared nine Spanish league titles between them, with only Atletico Madrid managing to interrupt that duopoly.
Both clubs start their campaigns Sunday with difficult away matches.
Barcelona return to Athletic Club's San Mames stadium, the site of the recent 4-0 humbling suffered in the first leg of the Spanish Super Cup.
Real travel to newly-promoted Sporting Gijon's El Molinon, a hostile environment that will prove a real test for Rafael Benitez in his first official match in charge after succeeding Carlo Ancelotti.
Both squads remain largely unchanged from those that came first and second respectively in the league last season, although there have been notable additions and departures for both sides.
The big change for Real is in goal as club legend and goalkeeper Iker Casillas ended his 25-year love affair with the club after moving to Porto.
Trying to fill Casillas' gloves will be 28-year-old Kiko Casilla -- signed from Espanyol during this transfer window -- who will vie for the number one sport with Keylor Navas, the Costa Rican goalkeeper signed after impressing at last year's World Cup.
A lackluster preseason has already hampered Benitez's early attempts to win over the fans and any early-season slip ups will surely be pounced upon by the media and the faithful alike.
"I'm from Madrid. I grew up here," said Benitez as he reflected on the pressure he could be under.
"I went to the Bernabeu two hours before my friends, to get a place in the third level, standing up. My childhood and youth were spent at this club. I know that coming second does not count."
In defense, Sergio Ramos and Pepe have both signed new contracts, the former another failed target for Manchester United during the transfer window.
Marcelo is expected to continue as the first choice left back, while Danilo -- a $36 million signing from Porto -- should occupy the right back berth ahead of Alvaro Arbeloa and Dani Carvajal.
The recent $38.5 million signing of Mateo Kovacic from Inter Milan will further bolster an already stellar midfield, with a likely starting three of Toni Kroos, Luka Modric and James Rodriguez to provide the most balance.
An attacking trio of Ronaldo, Gareth Bale and Karim Benzema looks as formidable as ever, while young stars Jese Rodriguez, Lucas Vazquez and Denis Cheryshev snapping at their heels.
Ronaldo's challenger to the Pichichi crown -- La Liga's top scorer award -- will, of course, be Messi. The Argentine eventually finished five goals behind Ronaldo last season, after the Portuguese's obsessive hunt for the FIFA Ballon d'Or came to fruition.
Messi will be supported by Neymar and Luis Suarez to complete the attacking triumvirate that notched 122 goals between them last season, surpassing the 118-goal record set by Ronaldo, Benzema and Gonzalo Higuain in 2011-2012.
But will Barca be short of attacking options following Pedro's move to Chelsea?
"Teams like Barca have this advantage: very good players leave and others arrive who adapt to help us in competition and so that we have a good level," defender Marc Bartra said Friday.
"When you have effective academy graduates together with the best in the world from outside the level is unbeatable."
It's not just Pedro that will be missing next season. Croat Ivan Rakitic will have even more responsibility as he attempts to fill the void left after Xavi's departure to Qatar.
Rakitic will be accompanied by the familiar faces of Sergio Busquets and Andres Iniesta, although Barca will have to wait until January before fielding new singing Arda Turan due to a current transfer embargo.
Aleix Vidal, signed from Europa League winners Sevilla, is another that will have to wait his turn.
"It took a lot of hard work to get here," said Vidal. "It required a lot of strength. But if you constantly work and believe in yourself, it is possible.
"I'm a fighter and I never throw in the towel, despite passing through a number of lesser-known clubs. Now I am here and I believe it is impossible to reach any higher."
In the right back spot he will be hoping to occupy, Dani Alves signed a new two-year contract after it looked all but certain that the Brazilian would be leaving the club.
Jordi Alba will keep his place on the opposite side of defense, while Javier Mascherano and Gerard Pique will continue as the first choice center back pairing, with Jeremy Mathieu the very able deputy waiting in the wings.
The Frenchman will start at least the first four games of the season, after Pique's foul-mouthed tirade at the linesman in the second leg of the Spanish Super Cup earned him a lengthy ban.
Chilean goalkeeper Claudio Bravo, fresh from his penalty-saving heroics in the Copa America final, will continue to battle for the number one spot with German Marc-Andre ter Stegen.
The chasing La Liga pack have all strengthened impressively this summer, despite Sevilla losing Vidal and Carlos Bacca, Atletico losing Turan and Valencia losing Nicolas Otamendi to Manchester City.
Atletico have added sought-after Colombian Jackson Martinez to its ranks, as well as resigning Filipe Luis after his one moderately successful season at Chelsea.
Sevilla have signed Ciro Immobile and Evgen Konoplyanka, as they prepare for the Champions League following last season's Europa League success.
Despite Otamendi's departure, Valencia still look strong. Promising left back Jose Luis Gaya remains at the Mestalla, while Athletic Bilbao -- with it's 5-1 aggregate Super Cup win over Barca -- has proven that the Spanish champions are by no means invincible.