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After advancing in the UEFA Europa League by bouncing Galatasaray in Istanbul on Thursday, Barcelona shift their focus to what will be a loaded slate on Sunday highlighted by El Clasico. Barca go to Real Madrid in a crucial game for both sides as Xavi's men look to start solidifying their top-four spot while Real aim to build upon their already comfortable position atop La Liga. Both teams enter in exceptional form with four straight league wins, but Barca are playing their best so far this season, giving the Blaugrana faithful a strong belief that they can go to the Bernabeu and win.

Over the last several weeks, Xavi has guided the team to numerous victories with consistency everywhere on the pitch. From his appointment in early November through January, his team averaged 1.1 goals per game. And in their last nine games entering this week, and with new signings gelling, they've averaged 2.7, scoring four goals in five of those games. Barca also are unbeaten in their last 15 matches.

Ahead of kickoff, here are three reasons why Barca have been able to turn it around:

1. Aubameyang has made all the difference

It's amazing what a quality striker can do. In a side that has struggled to find any sort of consistency in attack since Luis Suarez's best days, Pierre-Emerick Aubameyang has been the key to the attack, giving it a bite it lacked in a long time. The Gabon international only played 57 minutes in his first two games, which is understandable, taking some time to get fit and adjusted. But since then, he's been superb and it's a natural fit that feels like has been in existence for years now. 

With a renewed energy and confidence, the former Arsenal man has done it all, finishing from close and producing golazos from distance. He's got seven goals in his last seven games in all competitions, with a goal scored in five of them. Averaging a goal per game over the last month, him solidifying the No. 9 position has allowed for the team's other new additions to play their natural positions and give a revamped Barca attack some serious chemistry. 

2. Ferran and Traore are adapting quickly

With Aubameyang penned in as the No. 9, both Ferran Torres and Adama Traore have quickly found their footing as well. Since joining the team in the winter transfer window, Ferran has four goals and three assists and continues to return to form. His positioning has largely been superb, his runs have been precise, and though he has missed his fair amount of chances, he's been an impact player more often than not.

Adama, on the other hand, returns home to Barca. In a league not nearly as physical as England, the former Wolves star has used his speed and strength to his advantage, making defenses look silly time and time again. So far he's recorded four assists, and it wouldn't be a shock if that number is doubled by season's end. And when you considering that would be for half a season, that's some serious production.

3. Confidence and spirits are high 

You can have all of the talent in the world, but if you aren't on the same page and fostering a level of confidence, spirits are going to be low. Just look at the entire Barca era under Ronald Koeman. But now with Xavi, there is a different feeling with this Barca squad as the results have drastically improved. Bounced from the Champions League group stage, an early exit seemed likely until Xavi got things going. A top-four finish in La Liga seemed unrealistic, not what is unrealistic is them finishing outside of the top four.

Xavi has managed to change the culture quickly, with that, the team's trajectory has greatly improved.

"I'm very optimistic," defender Gerard Pique said, according to Marca. "After the months we went through and last season, to again take flight and see that we have a positive dynamic, it's the best possible news. People when they come to the stadium have fun, and that is primitive, and we do too on the pitch. The results will come, they have come, and we hope to continue on this path until the end of the season."

How to watch and odds

Date: Sunday, March 20 | Time: 4 p.m. ET
Location: Estadio Santiago Bernabeu -- Madrid, Spain
TV/Live stream: ESPN+
Odds: Real Madrid +110; Draw +265; Barcelona +235; O/U 2.5  (via Caesars Sportsbook)