When Valentine Colasante was called up to replace an injured dancer in the Paris Opera’s Don Quixote, a three-hour ballet that she had performed exactly once before, she didn’t even have time to be nervous.

“You don’t have a choice, you just go. You have to save the show and you feel yourself growing wings and your strength grows tenfold with the adrenaline,” she said.

Companies have to think about understudies even more in the age of coronavirus – just this week the Paris Opera had to cancel a Don Quixote performance because of an outbreak in its ranks.

But even before Covid, dancers would often drop out suddenly owing to illness or injury.

Colasante earned her stripes in the process: she was awarded the top “etoile” status at the end of her final performance and is back performing as the official headliner in the current run.

She likens it to the reserve footballer on the bench, called up to score the winner in a penalty shootout.

“You need calm and self-confidence. It’s the body that leads and the brain barely registers what is happening,” she said.

She had just three days to get ready.

“Just preparing your shoes, trying on the costumes and getting to know your partner – the three days are up already,” she said, laughing.

And often, they have much less time than that.

In October, on the opening night of the Paris Opera’s major production of The Red and the Black, star dancer Mathieu Ganio hurt himself before even the first act was over.

Within minutes, first soloist Florian Magnenet had taken his place and became the “saviour” of the production.

“Very quickly, you have to create magic,” Paris Opera Ballet director Aurelie Dupont said.

“Florian had learnt the role and was going to perform some of the other dates, but he found himself that night with a partner that was not his own,” said Dupont, herself a former etoile dancer.

“He was in the wings and had suddenly to find his costume, do his make-up in the intermission . . . so there was an element of stress.”

But she added that dancers in that situation were driven by a desire to save the show and all the work that the company had put into it.

Each company has its own system.

At the Paris Opera, Dupont prepares one or two top-tier understudies for the lead roles.

At London’s Royal Ballet, the dancers should be in the building for the half-hour call before the show begins, said artistic director Kevin O’Hare.

But sometimes they leave too early – as happens when ballet superstar David Hallberg injured himself midway through a performance in 2018, and his replacement had already gone home.

“I called Matthew Ball [the replacement], he called a taxi, put on his make-up, warmed up and danced,” said O’Hare. “It’s part of the job.”

Laurent Hilaire, ballet director for the Stanislavsky Theatre in Moscow, said he always keeps a couple of etoile dancers in the building in case of a problem.

“There was even one time when a dancer was watching the show in the audience and had to throw on her costume in five minutes. She had never performed the role, only rehearsed it,” he said.