The League leader, Super Cup champion and Cup semifinalist fought like a colossus on his return to Europe.
Barça was about to win a game that they refused to lose after a solemn moment from Rashford.
The Catalans never gave up, they corrected themselves and ended up dragging down the pompous United.
The tie remains open after an exchange of blows that moved the Camp Nou.
The European rhythm is more demanding than the Spanish one and Barça competed with integrity after losing the game due to Pedri's injury.
Ter Stegen, Koundé, Ronald Araújo, Alba (Alex Balde, min. 67), Marcos Alonso (A. Christensen, min. 66), Raphinha (Ferrán Torres, min. 82), Pedri (Sergi Roberto, min. 41), Gavi, Kessié Franck (Ansu Fati, min. 66), Frenkie De Jong and Lewandowski
MNU M United
De Gea, Wan-Bissaka, Tyrell Malacia, Varane, Shaw, Jadon Sancho (Alejandro Garnacho, min. 81), Casemiro, Fred, Wouter Weghorst, Bruno Fernandes and Rashford
49: Marcos Alonso.
58: Koundé (pp).
Yellow cards Alba (min. 30), Varane (min. 43), Casemiro (min. 65), Tyrell Malacia (min. 72) and Gavi (min. 73)
In the absence of the man from Tenerife, and also of Dembélé and Busquets, Barcelona appealed to the collective spirit in a very open, vibrant and even match, back and forth, out of control due to the lack of means, intense and with the unique environmental charge of the Camp Nou .
Although the challenge is the League, no one had any doubts that Barcelona will fight to look good in the Europa League.
It is not known how far the Catalans will go because now they depend on players who are difficult to classify like Raphinha.
Barça have a proud and rebellious Brazilian and United boast the quick and skilful Rashford.
The game went out of the script set by Barcelona since the victory against Madrid.
Xavi surprisingly moved his defense, the team's most stable line, and Ten Hag played with his attack in an attempt to seize the initiative at the Camp Nou.
The changes brought about an unpredictable duel that penalized Barça: Araujo-Jadon Sancho.
The Uruguayan had been moved to the right side, supposedly to overtake Rashford, and the Englishman had left the wing to sweep the attack front against the unprecedented pair of central defenders formed by Koundé and Marcos Alonso.
Rotations were not expected in such a demanding event and, nevertheless, the coach reserved Christensen and Balde to give entry to Marcos Alonso and Alba.
The Catalans stretched from the left wing and on the other hand they lost consistency and ease to get the ball out of Ter Stegen's area.
Risk situations alternated between the two goals in a dynamic and exciting match for the Camp Nou fans.
De Gea, however, was less required than Ter Stegen due to Barça's repeated losses.
The Barça goalkeeper responded in an extraordinary way in two goal plays against Weghorst and Rashford.
United's arrivals were neater and more frank than those of Barça.
The azulgrana did not give up in any case heading towards De Gea from the pressure, the recovery and the entries from Alba.
The English lose charm when they don't have the ball and are vulnerable defending De Gea's goal.
The Barca intensity, however, was too discontinuous, not very fluid and the game mechanics suffered more with the fall of Pedri.
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Lacking finesse, Lewandowski increasingly disfigured and reduced, forced to play with his back to De Gea's goal, Barcelona appealed to Raphinha's courage and outburst.
The Brazilian's shots are poisonous and his crosses from the corner are very tasty for central defenders like Marcos Alonso, who headed into the far post to surprise De Gea.
Barcelona scored from set pieces and the undetectable Rashford responded to the run.
The striker entered from the right side and shot at the goalkeeper's stick to score 1-1.
Ter Setegen hadn't been too successful for once against the fast-paced Rashford.
No blaugrana could stop the quick and skilled United striker.
Rashford astonished with a dribble that left Raphinha petrified to put the ball that made it 1-2 after being pushed by Koundé and then released from the Frenchman in a long run that did not end in a penalty, luckily for Barça.
The English unsuccessfully claimed the foul and Barcelona regained their spirits with the changes of Xavi and the entry of Christensen and Balde as well as Ansu.
The game went crazy and, surprisingly, Barça not only held on but reached the tie with a Raphinha cross that no one managed to reject or Lewandowski to dot;
claimed a penalty by the hands of Fred;
He finished off the post in a rejection by Casemiro and came close to victory with shots from Ansu.
Nobody asked for more from a decimated Barça and difficult to rebuild because Gavi will not play due to suspension at Old Trafford.
The return is even more difficult than the first leg because United looks like a very good team with Ten Hag.
Barça thinks more about winning the League and resisting in Europe.
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