The last time Barcelona won the Champions League and completed the treble was in the year 2015, a year which Cules will never forget. That year Barcelona ran riot in Europe and tore apart defenses for fun (courtesy of MSN). Since then Barcelona have not played up to their standard in Europe's most coveted club competition, failing to reach the semi-finals for 3 consecutive years.
Adding salt to their wounds, it is Barcelona’s eternal rivals Real Madrid who have won it for all the 3 years. This has been a major point of worry for La Blaugrana, as they are desperately aching for the trophy to come back to the Nou Camp. After their major exploits in the transfer market, it is clearly visible that the Catalans are going to do whatever it takes to regain their European dominance.
Therefore lets take a look at 5 things that will motivate Barcelona to win the treble this season.
#5 Revenge on Real Madrid

After Barcelona won the trophy last in 2015, Real Madrid have gained the upper hand in European Football by winning the competition 3 times in a row. Seeing their rivals have so much success has definitely inspired the LaLiga champions to overthrow them.
Real Madrid has certainly become better than Barcelona at club football’s grandest stage, something that hurts the supporters of the club to the core.
However, all this becomes easy for Barcelona, since the transfer of Real Madrid’s greatest player Cristiano Ronaldo to Juventus, they are comparatively weaker, and Barcelona can make the most out of it.
Thus taking revenge on Real Madrid will be one of the main reasons for Barcelona to win the Champions League, and complete the treble.
#4 Squad strength

La Blaugrana have reinforced their squad by adding the likes of Clement Lenglet, Arturo Vidal, Arthur Melo and Malcolm. Philippe Coutinho - the club's record transfer, and Ousmane Dembele - one of the most exciting young prospects in the world, are adjusting nicely to the playing style at the Nou Camp.
FC Barcelona has one of the strongest benches in the world and it is all because of a successful transfer market. Also the club has called some players who have completed their loan spells at other clubs like Munir El Haddadi. Ernesto Valverde has also placed his trust in young players like Juan Miranda and Riqui Puig of the Barcelona youth system by including them in the squad.
All this and with the likes of Lionel Messi, Luis Suarez, Sergio Busquets, Ivan Rakitic, Gerard Pique, and co in the squad, every club has to lookout for them wherever they play. With such a talented and experienced squad, Barcelona might just win the Champions League.
#3 Ambition

One doesn't need a genius level of thinking to see what would be the main aim of the Catalans. After going out in the same competition at the same stage for 3 consecutive years, Barcelona have set their goal in mind, and have to play at an elite level to claim the European Crown.
Ahead of the Joan Gamper match, Barcelona skipper Lionel Messi gave a speech to Barcelona fans, promising to fight for the Champions League.
"We have a squad to get excited about, those who have arrived will help us to improve a lot and if last year was very good with the Copa and LaLiga, its true we have remembered what happened to us in the Champions League with our elimination, and this year we will do everything possible to bring this beautiful cup back to Camp Nou"
The above mentioned statement is a clear threat to all the clubs in Europe that only Barcelona are going to win the trophy, and they will demolish anything that comes in their path.
#2 Lionel Messi

Lionel Messi - no words are left to describe the genius of this little man. As Pep Guardiola rightly said,
“Don’t write about him. Don’t try to describe him. Just watch him”
To win the Champions League Trophy, the Catalan side requires a source of inspiration, a saviour to save them in complex situations, and fortunately they have the exact man who wears the number 10 jersey on his back.
After Messi was snubbed (wrongly) off the FIFA’s Best list despite having a fantastic season and winning the domestic double, he must have realised that he has to improve his game, raise it to a whole new level, and perform consistently at a stellar rate to make sure Barcelona wins all the 3 trophies.
With 4 goals and 2 assists to his name already in just 3 matches, the maestro will be looking forward to taking his incredible form into all the tournaments this term.
On his day he can make the best defenders look like they are lost, and tear down big teams like they are Sunday league teams. With the attacker on the team, there is no doubt the Catalans have a big chance of winning the treble this time around.
#1 UEFA Champions League priority

BARCELONA HAS TO WIN THE CHAMPIONS LEAGUE!!! It is now a matter of prestige for the Catalan club, hitting back on all the insults that they have tolerated for 3 full years.
Winning the Champions League is no small deal, and doing it three times in a row certainly isn’t luck. And Real Madrid has done it thrice in a row. Real Madrid paid a heavy price in last season's LaLiga to maintain their Champions League title, and as a result they finished 3rd in the table with 76 points, taking them 18 points below their arch rivals Barcelona.
The staff at the Madrid club may have shifted their priority to domestic success, and not European success. On the other hand Barcelona has set the Champions League as their priority.
Ernesto Valverde must give rest to important players during easy fixtures, saving them for important ones, thus not putting a strain on them and allowing them play to their fullest potential.
Which in turn will result in other players getting play time. He must have one goal in mind, and that is to win the UCL. Because LaLiga and Copa Del Rey aren’t big problems for Barcelona, it's the Champions League that has caused problems.
Thus prioritising the Champions League will be one of the main things that will lead Barcelona to a treble winning season.