Jose Mourinho's side created the majority of the openings at Santiago Bernabeu, but Guardiola's men escaped with a draw ahead of Wednesday's return clash
Mesut Ozil gave the capital giants the lead, but Barca stormed back with goals from David Villa and Lionel Messi. Xabi Alonso levelled the match in the second-half, and the teams couldn't be separated.
With first-choice centre-back pairing Carles Puyol and Gerard Pique both sidelined, the visitors were forced to play with the unfamiliar duo of Eric Abidal and Javier Mascherano at the heart of defence.
Additionally, Thiago Alcantara was given a place in the starting line-up in lieu of Xavi, while new signing Alexis Sanchez was given a baptism of fire against the Catalans' Clasico rivals. Meanwhile, Jose Mourinho opted to use the exact same XI that lost 5-0 at Camp Nou last season.
The hosts got the heated affair underway, and very quickly it looked as though Madrid were the hungrier of the teams for victory. Cristiano Ronaldo, looking fitter than ever, shot off down the left flank, finding himself enough space to weight a beautiful cross for Karim Benzema. The Frenchman's connection was weak, however, allowing Victor Valdes to make an important save.
Mourinho's men continued to control the tempo of the game, and their domination of possession would soon pay off. After just 13 minutes, Benzema, eagerly getting himself involved again, strode towards goal, picking up markers as he went.
Carefully watching the former Lyon man's run, Ozil found himself space in the box, allowing Benzema to provide the German with the assist that would open up the game. Finishing from close range, Mesut Ozil neatly put the ball low and hard past Valdes to give the hosts a well earned lead.
Mesut the man | Ozil opened the scoring for MadridAs Barca struggled to get out of their own half, centre-forward Lionel Messi dropped deeper to get his first few touches of the ball – touches that would soon prove pivotal.
Picking the ball up just past the half-way line, the Argentine pinged forward a perfectly weighted through-ball for David Villa, who was surging down the left. Executing a neat cut-back, Villa turned and skipped inside before curling a world-class effort around Iker Casillas to restore parity for the Catalans.
Just before half-time, more good work down the left from Ronaldo almost saw the Portuguese luminary score one of his own as Madrid continued to boss, but Barca would soon vocalise their retort for a second time, through Messi.
In one of the few attacks that saw Barcelona in Madrid's final third, Messi shook off no less than three markers before finding himself half a yard to shoot low and hard past Casillas, putting the visitors in the driving seat going into half-time.
As the teams began the second-half, it would be the Spanish champions who looked the sharper of the two sides, perhaps buoyed by their goal advantage, but the new-found enthusiasm wouldn't last long.
Barging their way back into the game, Madrid earned themselves a corner five minutes into the second session. Ozil whipped the ball in at the front post, and it was Pepe who would tee-up goalscorer Xabi Alonso to strike from the edge of the box. Finishing with great power through a sea of bodies, the Spain international brought the game back to level pegging.
Madrid's monopolising of possession continued, leading to a selection of golden chances for the capital side. Jose Callejon watched as his assist for Ronaldo sailed over the bar following a volley, while Ozil looked on as his cross for Benzema was one again met with a tame header. For all their dominance, Madrid couldn't seem to capitalise on their chances.
The remaining minutes witnessed a pair of big decisions for the referee, who was forced to make a penalty call at either end of the pitch. Ronaldo screamed for a spot-kick after an altercation with Valdes, while Pedro went down under a challenge from Marcelo. The referee was unmoved, however, and a thrilling encounter was brought to a close.
Jose Mourinho will be unhappy that his men don't have the advantage, but will undoubtedly be aiming to finish the job in the second-leg.