Marco van Ginkel's first season at Chelsea has been wrecked by a knee ligament injury which will rule out the midfielder for around nine months and has ended his hopes of playing for Holland at next summer's World Cup.

Scans confirmed day that Van Ginkel tore an anterior cruciate ligament in the opening 10 minutes of Chelsea's Capital One Cup victory at Swindon Town. The lengthy absence is a cruel blow to the £9m summer signing from Vitesse Arnhem and a significant one for Chelsea's manager, José Mourinho, too.

The 20-year-old is highly rated by Mourinho and could have expected to feature regularly in his debut season. His absence limits Chelsea's options in central midfield, where only Frank Lampard is a similar type of player.

Chelsea's match at Swindon gave opportunities to impress to players who have been out of favour, among them David Luiz and Juan Mata, who reacted bullishly to the challenge from the manager.

David Luiz, whose own performance against Basel the previous week had drawn criticism from Mourinho, was also effective at centre-half and after the interval, in midfield. "We don't need to prove anything: we just need to show that everyone wants to play," the Brazilian said. "Everyone had an opportunity to play, and you want to show your football. This is a big club with many, many good players.

"If we just had 11 players you cannot win anything. It's natural. Last year there were seven players left on the bench, and next year it will be the same. This year the boss chooses his 11 players to play and his philosophy is to do the best job for Chelsea. For me that is normal.

"How do you know I was left out [against Fulham on Saturday]? When other players are left out of the team people say nothing. I don't need to prove anything. Everyone knows who David Luiz is. I want to play football and enjoy myself on the pitch, so when I have an opportunity to play I want to enjoy it. I am just one more player in the team. Sometimes the manager puts me in, sometimes not, so it is his choice."

David Luiz insisted Mourinho has not asked him to curb his desire to play out from the back, even if his penchant for flamboyance has occasionally seemed risky. "He has just asked me to play my football with high intensity, a high attitude from the start, like all the players," said the defender. "He is a manager who wants everyone to work hard, not just David Luiz. Everyone." The same cannot be said of Mata, who has been asked to adapt his game to play wider, alongside Oscar, and incorporate more defensive discipline into his style.

"It's easy for me to focus on football and just do what I have to do," Mata said. "The only thing I have in my mind is to keep working, keep training hard, keep improving as a player and keep scoring and making assists. That's what I did [against Swindon]. I've played in three different positions. In the beginning I was playing as a left-winger, then on the right and last season as a No10. I feel comfortable playing in any offensive position. It's better if a player can play in lots of different positions rather than just one."