Isco sustained the injury in the second half against the Catalan side but managed to complete the full 90 minutes as the newly promoted outfit came from behind to secure a 2-1 victory over Zinedine Zidane's men at the Estadi Montilivi.
The Spain international opened the scoring for Real after 12 minutes but two quick second-half strikes from former Middlesbrough forward Cristian Stuani and Cristian Portugués Manzanera stunned Los Blancos, who are now eight points behind league leaders Barcelona, who secured a 2-0 win over Athletic Club Bilbao on Saturday.
The news of Isco's knock will no doubt worry Real, who could be without Mateo Kovacic, Dani Carvajal, Keylor Navas, Raphael Varane and Gareth Bale for their visit to Wembley, but the 25-year-old expects to be passed fit to face Tottenham, who may be able to call on Harry Kane after the forward missed the 1-0 defeat by Manchester United with a minor hamstring problem.
"I have a problem. I've been hit, but by Wednesday I'll be back," Isco told Mundo Deportivo.
The defeat to Girona, currently enjoying their first season in the top-flight of Spanish football since being founded in 1930, has left Real Madrid third in La Liga, behind arch-rivals Barcelona and Valencia.
Isco, who has featured in all of Real's 10 league matches so far this season, was infuriated by the way Girona were allowed to take the lead and has called on his teammates to find an extra source of motivation as they bid to get their season back on track.
"Maybe we lacked a bit of attitude at the start of the second half, they have come back very easily" Isco said. "The league is not dead for Madrid, but I hate that we missed three important points. I do not think it's a problem to run more, when you are in the field you always want the best for the team.
"You have to reduce disconnections, because any team can hurt you. Concentration has to come out naturally. We have to be more motivated, we should not give our rivals any opportunities."
If fully fit Isco will no doubt start against Tottenham, a team he could well have signed for a couple of years ago. The north London outfit were keen on prising the former Malaga star out of the Spanish capital when he was no more than a rotation option at Real, but a deal never came to pass.
Real Madrid have a number of injury problems ahead of the clash at Wembley, but Tottenham are not blessed with a clean bill of health either. Along with the doubts of Kane's fitness, influential midfielder Victor Wanyama has been sidelined with a nasty knee problem, while it is not known when Erik Lamela will return from his troublesome hip problems.