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Germany international Ter Stegen underwent a successful operation after suffering a complete rupture of the patella tendon in his right knee.

The 32 year-old suffered the injury in Barca's 5-1 win at Villarreal in LaLiga and is expected to be out for at least eight months, according to Spanish media reports.

Despite Ter Stegen's season likely being over, Flick is remaining upbeat, backing academy product Pena to handle the step up.

"Inaki is doing very well, in pre-season too. He has worked very hard to be here. He is focused and ready to play," Flick said ahead of Wednesday's home game versus Getafe.

"We are confident but we also have to look at what we do because the players at the back are very young. For the moment, we don't feel under pressure and we trust in Inaki."

Having joined Barcelona's La Masia academy aged 13, 25 year-old Pena has made 23 first-team appearances, conceding 39 goals and keeping five clean sheets.

Pena made 10 league appearances for Barca last term, with his save percentage of 56.4 percent falling some way short of Ter Stegen's 73.5 percent.

Pena also conceded 17 goals from 13.89 expected goals on target (xGoT) faced, giving him an underperformance of 3.1 in terms of goals prevented. Ter Stegen, by contrast, conceded 27 times from 27.84 xGoT faced.

The Catalans were already without new signing Dani Olmo and fellow midfielders Gavi, Frenkie de Jong, Marc Bernal and Fermin Lopez, plus defenders Ronald Araujo and Andreas Christensen, due to injuries.

However, they have made a perfect start to the season under Flick, with six straight wins putting them top of LaLiga, four points ahead of reigning champions Real Madrid in second.

But the former Bayern Munich boss is striving for more, adding: "We analysed the game against Villarreal and we saw a lot of things that can be improved. 

"We haven't reached the end of the road. You can always do more. We are moving forward step by step."