Frenkie de Jong will miss the start of Barcelona's season after it was discovered that he had suffered a medial collateral ligament (MCL) tear while representing the Netherlands at the World Cup.

De Jong was one of seven players to start all four of the Oranje's games at the World Cup, as they impressed in the groups but then lost to Morocco on penalties in the last 32.

Only centre-backs Jan Paul van Hecke (343/371) and Virgil van Dijk (333/356) attempted or completed more passes for the Netherlands than De Jong (217/233), though he only created two chances from a deep midfield position.

On Thursday, Barcelona confirmed in a statement that De Jong had sustained a knee injury at the tournament, which reports said could sideline him for several months.

"Medical tests have confirmed that De Jong has suffered a tear of the medial collateral ligament (MCL) in his right knee," the Blaugrana said in a statement.

"The player will continue to undergo treatment under the supervision of the club's medical staff, with his progress to be assessed over the coming weeks."

De Jong later took to social media to clarify that he will not have to undergo surgery, while hitting back at suggestions he aggravated the injury by playing through the pain barrier at the World Cup. 

"Normally, I don't pay much attention to what is being written about me, the team or the club. But recently, there's been a lot of speculation about my injury and my situation at Barca," De Jong wrote on Instagram.

"It's difficult for me to see people questioning my relationship and commitment to the club because of false reports. Football is everything to me, and I have always given everything I have for FC Barcelona and my country. I am now fully focused on my recovery and returning to the pitch as soon as possible.

"During the World Cup, I injured my knee. After the first assessment, the doctors told me it was a small injury and that it wouldn't get worse if I continued playing.

"The only challenge was playing with some pain, but throughout my career I have done that whenever I could contribute to the team, both for my club and my country.

"Further examinations showed that the injury was more serious than initially determined. Thankfully, at this stage there is no need for surgery, and I am now fully focused on my recovery and returning to the pitch as soon as possible."

De Jong looked to be limping when he was substituted during extra time against Morocco in the round of 32, as the Netherlands failed to reach the quarter-finals when participating at FIFA's flagship tournament for the first time since 1990 (failed to qualify in 2002 and 2018, lost in round of 16 in 1990).

De Jong will now be absent when Barca begin their LaLiga campaign away to Elche on August 23, looking to win a third straight domestic crown under Hansi Flick.