Casemiro
Casemiro has proven to be a key player for Zinedine Zidane.Reuters

Alarms bells are ringing at Real Madrid following the news that the duo of Karim Benzema and Casemiro were unable to take part in a Tuesday training session, just a day before the Champions League semi-final second leg against Manchester City on 4 May. In better news for the club, Cristiano Ronaldo looks set to return to action for the crunch tie after the Portuguese star completed the workout with the rest of the team, as he did on Monday.

"[Zinedine] Zidane's men finished their preparation for this Wednesday's decisive match, in which they'll be looking for a victory to take them to the Champions League final. Borja Mayoral trained with the first team, while Benzema and Casemiro worked inside," Real Madrid confirmed.

Benzema suffered a "muscle injury in his left hamstring" during the goalless draw at the Etihad Stadium last week, being replaced by Jese Rodriguez at half-time and subsequently missing the La Liga 1-0 victory over Real Sociedad. Zidane reported on Friday that he hoped both the Frenchman and Ronaldo would be fit to host City on Wednesday. However, doubts over Benzema's availability have grown after the club revealed the striker couldn't take part in the Tuesday workout, after he already missed Monday's session.

Casemiro, meanwhile, completed the full 90 minutes at Anoeta Stadium but was a surprising absentee from the Monday workout, with Real Madrid revealing he had picked up a knock. Early reports suggested his absence in the Monday workout was just a precaution, but doubts over his participation in the Champions League semi-final second leg have been sparked after the Brazilian also missed Tuesday's training.

The absence of the duo against City will be a big blow for Zidane, as the French striker is the club's second top scorer while the Brazilian has been an integral part of the club since Zizou took over, holding the midfield to give more freedom to Luka Modric and Toni Kroos to shape the game behind the BBC trident.

Lucas Vazquez could fill in for Benzema in attack, but Zidane will need to restructure his midfield with a more attacking option such as Isco or James Rodriguez should Casemiro miss the game. This would force Kroos into a deeper role, as he played in under Rafa Benitez earlier this season, much to common criticism. Casemiro was expected to be a key figure in the game as he would be expected to help stop Manchester City's counter-attack threat.

The news is more positive over the Ronaldo situation though. The Portuguese ace missed both the first leg against City and the weekend visit to San Sebastian after he picked a muscle strain in his right thigh during the 3-0 victory over Villarreal on 20 April. However, it looks like he will be available for the European decider after he returned to training on Monday, while also completed the session on Tuesday morning.