Five players to look out for in the UEFA Champions League semi-finals

The semi-finals of the UEFA Champions League will take fans on a rollercoaster ride as Europe's four giants try to outsmart each other in two-legged ties. The stakes are high this term for Barcelona who face a Bayern Munich side managed by Catalan legend Pep Guardiola. Real Madrid meanwhile face a tough task against Italian champions Juventus, who on paper will start the clash as underdogs.

Pep Guardiola found enormous success with Barcelona both as a player and coach. He now faces the prospect of plotting the downfall of his beloved club.

Last time the two sides met in the Champions League was in 2012-13, where eventual winners Bayern thrashed Barca 7-0 in the two-legged semi. Jupp Heynckes was the manager of Bayern at that time, while the late Tito Vilanova was in charge of the Catalans. This term sees two former Barca teammates Luis Enrique and Pep Guardiola trying to outthink each other.

Real, who are eyeing successive Champions League honours, know that their rivals from Turin will be a tough nut to crack. What matters for both teams is the return of key players from injuries. Juve are back in the semis fold after a period of 12 years and they will be desperate for success this time around.

The four teams have won the competition 21 times between them and that statistic offers enough evidence of the history of these great clubs.

As the European giants prepare to battle, we look at five players who hold the power of determining the fortunes of these ties.

Lionel Messi (Barcelona)

Barcelona will be spearheaded by the Argentina international once again as the Spanish leaders aim to dominate proceedings on the big stage. Messi has been influential for the Catalan giants in the European competition this time too, and he will look to add more feathers to his cap in the semis against a high pressing Bayern side.

Barcelona booked a semi-final berth for the third time in four years. Messi was brilliant against Paris Saint-Germain in the quarter-final this year and his form has been superb across all competitions.

Messi recently bagged his 400th goal for Barcelona and has scored five goals in the Champions League so far this term. The Barca ace is in prime position to end up as the highest scorer in the competition.

Cristiano Ronaldo (Real Madrid)

Cristiano Ronaldo like Lionel Messi is the trump card for his side. The defending champions will thank the Portuguese for a superb display against rivals Atletico in the quarters. Ronaldo made a fine assist for Javier Hernandez whose goal determined the outcome of Real's progression over two legs.

Ronaldo has scored eight goals in the Champions League this season and will look to add to his tally against Juventus.

The former Manchester United player scored his 50th goal of the season recently to achieve the feat for the fifth successive term. Carlo Ancelotti is eyeing a fourth title and Ronaldo will play a big role in determining Real's fortunes to be the first team to successfully defend their title.

Thiago Alcantara (Bayern Munich)

The former Barcelona player had a forgettable season after being out with injury for over a year. After making a comeback in two successive matches as a substitute, Alcantara started the game for Bayern in the Champions league game against FC Porto in the quarters and scored a goal for the visitors.

A week later he scored once again in Bayern's 6-1 romp at home. Alcantara has looked sublime for Bayern in the two crucial matches and will play a big role for Pep Guardiola's side in the semis. The Spaniard's passing abilities and calmness on the ball is a big help in linking the play in midfield.

Alcantara has come back from injury at the right time for Bayern and Pep will hope for another good performance in the semis from the midfielder.

Carlos Tevez (Juventus)

The Juventus forward has been the Italian giants' main man and has been influential in his side's superb performance in the knock-out rounds. Tevez has been the highlight of Juve's success after having notched 26 goals for the Italian champions this season including six goals in the Champions League.

Juve will depend on Tevez to shine for them on the big stage as the Serie A team has managed to book a semis berth after a long gap of 12 years. Tevez's contract expires in 2016 at Juve and he has recently denied claims that he will be quitting the club this summer.

Irrespective of all the speculation, Tevez remains a key player for Juve and he will pose a huge threat for opposition defense.

Thomas Muller (Bayern Munich)

Not many players can consistently deliver on the big stage like Thomas Muller can. The Bayern Munich forward has scored six goals for his side this term in the Champions League and 20 overall across all competitions in 2014-15 season.

Muller's experience and versatility is key for Pep Guardiola and his overall impact on the game for Bayern is of great value. His extraordinary celebrations with the fans after Bayern's 6-1 win against FC Porto at home not only showcased his passion for the club, but also his ability to connect with the Allianz Arena faithful despite the club boasting of some big name players.

Muller's strength lies in his physical approach. Apart from being a constant runner, he is one of the best attacking players in the world. With the return of several key players from injuries, Muller will relish the prospect of helping Bayern enter yet another Champions League final.