Sergio Ramos faces a battle to be fit for Real Madrid's Champions League opener against Shakhtar Donetsk with head coach Zinedine Zidane set to make a call on his availability on Wednesday.

Los Blancos captain Ramos took a knock to his knee in Saturday's shock 1-0 LaLiga loss to Cadiz and was absent from Tuesday's training session ahead of the fixture at Estadio Alfredo Di Stefano.

With the first Clasico of the campaign against Barcelona taking place this weekend Zidane is unlikely to risk exacerbating the issue and the Frenchman plans to see how his skipper is on game day.

"There's an issue with Sergio Ramos, he hasn't trained with the team," Zidane told a pre-match news conference on Tuesday.

"We won't take any risks with the players; the players have to be fit. He's got a knock, we have to wait and see how he feels, it's true today he didn't train at the same tempo as his team-mates."

While Ramos is a fresh injury concern, forward Eden Hazard – whose time at Madrid has been blighted by fitness woes – remains a longer-term absentee.

The Belgium international, who is yet to feature this campaign, was set to return to action last month but sustained a muscle complaint during his recovery from an ankle injury.

Offering an update on Hazard, Zidane said: "Eden has been back out on the training pitch but that injury was a bit more than we hoped.

"He's in good hands and hopefully shortly he'll be back and he'll back to stay fit and hopefully he'll be able to play for the full season without further setbacks."

Hazard may be low on luck, but his Belgium team-mate Thibaut Courtois has been in sensational form for Madrid.

Of the previous 43 shots on target he has faced in LaLiga, Courtois has saved 38 and his stats for his season show he has kept out 16 of the 19 efforts on target.

Asked to explain Courtois' performances, Zidane said: "I think Thibaut Courtois has always proven his worth. He's a great goalkeeper.

"I think he just needed some time to adapt to the demands of playing for such a big club. No one ever doubted his talent.

"We see he's improving every day, it's great for the team, great for Thibaut. If everyone can play at 100 per cent, we'll be a tough side to beat. That is our objective: to play at 100 per cent every game."

Madrid were well below their best against Cadiz, mustering just two shots on target despite having almost 75 per cent of the possession.

Zidane's side have scored just six goals in five LaLiga games but the coach, while accepting his team deserved the criticism that came their way, said there will be plenty of peaks and troughs in a busy campaign.

"I think we deserved the criticism as published following that defeat, but now it's our opportunity to turn the tide, turn that corner and hopefully you'll see a different Real Madrid," he said.

"I think whenever things have been tough, this team have stepped up and produced the goods. There are moments during the season when there are dips in form.

"The other day we could have done things better and I'm convinced we can do things better.

"I think you have to look at the bigger picture. If you look at not just us, others too, no clubs have started in brilliant fashion, teams have struggled. There will be days when we do things very, very well."