The latest meeting between Barcelona and Real Madrid on Tuesday presents yet another enticing clash between the world’s two greatest players, Lionel Messi and Cristiano Ronaldo, however both clubs have issues to overcome relating to their star men ahead of the second-leg of their Copa del Rey semifinal.

The first leg between the two sides, now almost a month ago, was notable for being a rare Clasico in which neither of the game’s superstars found the back of the net. It would be a significant surprise if the tie ended with that still being the case, but all is not in full harmony with either Barcelona or Madrid and their respective stars.

Real Madrid’s issues are well established. Sitting 16 points behind their fierce rivals in the Liga standings, any realistic hope of retaining their title have long-since disappeared. Within the space of the next week all meaning to their season could also vanish into the Madrid night.

After the Copa del Rey matchup comes the return-leg of their finely balanced Champions League tie with Manchester United, sandwiching the second league Clasico at the weekend.  It is the cup competitions that hold Madrid’s only chances of redemption this season after a tumultuous campaign both on and off the pitch.

While Los Blancos have lacked the intensity of their relentlessly consistent performances last season, there have also been widespread reports of unrest between manager Jose Mourinho and some of the club’s most experienced players.

Added to these matters has been growing speculation about the happiness or not of their talisman, Ronaldo.

Ever since the Portuguese forward admitted to being unhappy, and that the club knew why, back in September, speculation has swirled over his future. In the past week, sections of the British press have strongly linked him with a summer return to Manchester United. Much of Ronaldo’s discontent is believed to stem from what he perceives as a lack of public backing from his club when compared to the support given by Barcelona toward Messi.

The frustration of the constant stream of awards and plaudits racked up by Messi appear to have, perhaps understandably, got under Ronaldo’s skin. He would doubtless love the chance to outshine the four-time Ballon d’Or winner on Tuesday as he did in the crucial Liga title decider last season. Indeed , Ronaldo has scored on his last five visits to Camp Nou. 

Despite their dominance in the league this season, all is not going wholly smoothly at Barcelona, either. The surprise first-leg Champions League defeat to Milan last week exposed a decline in their performances that has been present without serious consequence for several weeks.

Much of the problems have been carelessness without the ball, but, as was shown four weeks ago against Madrid and also in defeat to Milan, Barcelona are also having difficulty penetrating in attack.

Messi was largely ineffective in both those matches and while some of that must be put down to the forward being just short of his best, he also suffered from the lack of threat around him.

Alexis Sanchez’s drought of confidence has been increasingly, painfully apparent as the season has progressed, Pedro—so prolific for Spain this season—has too often misfired in front of goal, while David Villa has been used infrequently and has missed time recently with kidney stones.

Those issues have allowed opposition defenses to focus even more attention on negating the space afforded to Messi, on whom Barcelona’s reliance has perhaps trickled into the realm of unhealthy of late.

There were encouraging signs on Saturday against Sevilla, when David Villa started and got himself on the scoresheet. Having been linked with a move away in January after falling down the pecking order following his return from a broken leg, Villa could now play a crucial role in Barcelona and Messi’s form to the end of the season—beginning with the tantalizingly poised second-leg with Real Madrid on Tuesday.