Gareth Bale
Gareth Bale was forced off during Real Madrid's 3-1 victory over Borussia Dortmund. Getty

Real Madrid star Gareth Bale is a doubt for the upcoming clash with Espanyol on Sunday (1 October) having been unable to train since being forced off during Tuesday's 3-1 victory over Borussia Dortmund.

The potential absence of the Welshman is a new concern for Zinedine Zidane as the visit of the Catalan side will also come too early for Karim Benzema, Marcelo, Theo Hernandez,and Mateo Kovacic.

Cristiano Ronaldo also missed Thursday's workout, but the reigning Ballon d'Or should be fit to lead Los Blancos attack against the Barcelona-based side after the club confirmed that he was back in training on Friday morning.

"The squad went through the penultimate training session before welcoming Espanyol to the Santiago Bernabéu (Sunday, 8:45pm CEST). Cristiano Ronaldo returned to the group for a session where high intensity ball work was the focus," the club confirmed.

"The Whites started with passing and control exercises and practised possession and pressing divided into two teams. Afterwards they played several games in reduced spaces. Bale worked inside the facilities, while Kovacic, Marcelo, Theo and Benzema continue with their recovery processes. The last two were out on the pitch performing specific exercises alone."

Bale delivered arguably his best performance of the campaign during the victory over Dortmund, opening the scoring with a superb volley before setting up Cristiano Ronaldo for the second goal of the game.

However, the Welshman set alarms bells ringing at Real Madrid with five minutes remaining after being forced off and replaced by Lucas Vazquez due to cramp.

"I hope that there are more turning points like tonight's, but Gareth is now on really good form. His calf has swelled up but it's nothing major," Zidane said in a press conference following the victory over Dortmund.

"He hasn't had it easy and I'm delighted for him. Getting a goal like that is fantastic for him. This game will have done wonders for him and if you give him the space he's lethal, he's just so good."

On Thursday reports in Spain said that subsequent scans ruled out a muscle injury, with the player suffering only a slight strain on his left thigh.

However, his availability for the visit of Espanyol looks uncertain as he was unable to complete full training on either Thursday or Friday.

Bale will still have another workout on Saturday to prove his fitness, but Zidane may consider resting him anyway after the Welshman international struggled with various injuries during much of last campaign.

Furthermore, Zidane has Marco Asensio ready to take his place in the line-up after the Real Madrid starlet was rested against Dortmund.

Ronaldo, Isco and even young Borja Mayoral could complete the attack, but long-term absentee Benzema will remain on the sidelines alongside Marcelo, Theo and Kovacic.

One way or another Bale is expected to be fit to join Wales ahead of the World Cup qualifying matches against Georgia and Republic of Ireland to be played on 6 and 9 October.