MADRID, July 19 (Xinhua) -- Real Madrid's injury prone pre-season continued on Monday with the news that goalkeeper Thibaut Courtois is in danger of missing the start of the season after injuring his left ankle.

The Belgian international, who only last week said he now felt he was the number one goalkeeper at the club, suffered the injury in a collision in training before the Real Madrid squad flew to Munich to play in the Audi Cup.

Courtois was left out of the squad which travelled to Germany and will subsequently face beaten Champions League finalists Tottenham Hotspurs on Tuesday.

The Real Madrid website confirmed the injury, reporting that the keeper had suffered a "grade two" twist on his left ankle and that his return to action "depends on how it evolves".

Courtois is the latest in a long line of players to suffer injuries in what has been a difficult pre-season for Zinedine Zidane's side.

Forward Marco Asensio will miss nearly all of the campaign after tearing the meniscus and cruciate knee ligaments in his knee, while new signing Ferland Mendy is also out of action for around a month with a thigh injury.

Youngster Brahim Diaz is also sidelined after suffering a muscle injury which rules him out for pre-season, while another new arrival, Luka Jovic has also been left out of the squad that travelled to Munich after hurting his ankle in Saturday's 7-3 thrashing by Atletico Madrid.

Real Madrid have yet to win a pre-season game in open play this summer, also losing 3-1 to Bayern Munich and drawing 2-2 with Arsenal before beating the English side in a penalty shoot-out.

Gareth Bale has also been left out of Real Madrid's latest squad, which will provoke further speculation about the Welshman's future.