The 26-year-old, who won the International Ski Federation (FIS) Nordic Combined World Cup Triple in January, had just returned from a partial ACL tear he picked up during his home World Championships in Seefeld.

He was making his second training jump back at international competition level when his left knee collapsed on impact of landing a 134.5 metres jump, leading to a crash.

Seidl was transported to Maria Hilf Private Hospital in Austrian city Klagenfurt, where preliminary examinations resulted in a possible new ACL rupture.

He was then taken to Klinik Diakonissen Linz to undergo a medical radiation technologist scan.

The result confirmed the preliminary diagnosis of an ACL rupture, as well as a meniscus injury.

Seidl underwent surgery on Saturday (September 7).

"Mario’s knee surgery went well," Dr Jürgen Barthofer said.

"We treated the ACL surgically and removed parts of the meniscus and a small cartilage damage.

"Mario will be able to leave the hospital on Monday (today) but due to his injuries, he will miss the entire upcoming season."

Seidl produced a remarkable comeback to win the FIS Nordic Combined World Cup Triple in Chaux-Neuve in France.

He recorded two huge jumps and enjoyed a near-flawless 15 kilometres cross-country race to seal arguably the biggest victory of his career.