Buckle up. We're in for an intense match.

The fourth match of a five-match series starts Wednesday when long-time foes Real Madrid host Barcelona at Santiago Bernabeu in the first leg of the Champions League semi-final.

The two La Liga giants met three times earlier over two competitions, starting with a 5-0 Barcelona thumping back in November. That match was followed by the two matches within the last two weeks that resulted in a 1-1 draw, and 1-0 overtime Real Madrid victory to take home their first Copa del Rey title in 18 years.

Tonight the stakes might be at their highest as the winner of the two-match series advances to the Champions League Final to play either Manchester United or Schalke 04 in Wembley Stadium.

Defenders Maxwell, Adriano, and Eric Abidal will be sidelined, as well as forward Bojan Krkic. Those losses hurt, but not as bad as losing midfielder Andres Iniesta, who is nursing a calf strain.

But fortunately for Pep Guardiola, Carles Puyol is likely to start after recovering from a hamstring injury, and will be joined in the back with Gabriel Milito.

Jose Mourinho's squad is less hobbled. Only Sami Khedira is injured, though Ricardo Carvalho is out due to suspension.

Real Madrid will likely try to duplicate their performance in the Copa del Rey by trying to play an ugly style and counter-attack. Mourinho will have to juggle his bench players, as Karim Benzema, Emmanuel Adebayor, and Gonzalo Higuain may be needed if Cristiano Ronaldo needs help up front.

The difference in Wednesday's match might be Lionel Messi. Real Madrid defender Pepe will be called upon to neutralize the Argentine star, but considering the reigning Ballon d'Or winner has not scored a non-penalty goal in three matches against Real Madrid, it will be a tough task.

For Real Madrid, another great performance from Ronaldo could be the only way to beat Barcelona. The Catalans will have a chip on their shoulders to avenge the Copa del Rey loss, and to beat their rivals. Indeed, this will be an inspired Barcelona squad.

Real Madrid know they need a win, and to not concede an away goal. The second leg will be in Camp Nou, and the 5-0 loss is still likely to be on the minds of Los Galacticos.

Expect another physical and intense match. Real Madrid can't afford to come out of this match without a goal, so they can go to Camp Nou with an edge.

Barcelona will continue to attack, and get some much-needed help from defender Dani Alves. But the more Barcelona pushes, the more vulnerable they will be should they turn the ball over. With a lack of depth in defense, Guardiola needs to instill in his players that Real Madrid's attack needs to get frustrated by the midfield.

A tie of any kind would be a good result for Barcelona, but judging by the way they've dominated opponents this season, Barcelona has a win on their minds.

Barcelona has a superstar in Messi who will be playing with an added incentive to shine. Will that be enough?