Hansi Flick pulled off more football wizardry in Barcelona's 5-1 thrashing of Villarreal on Sunday. Like all good magicians, though, it's time for him to swirl his cape, twirl his moustache, look the audience straight in the eye and announce, "And now for my next trick!"

The German coach's Sunday sorcery was a devastating performance in which his team could easily have scored five or six more, against a difficult rival, using three more youngsters in the Barça lineup who, between them, had a mere five LaLiga starts for the club: Gerard Martín (2), Sergi Domínguez (1) and Pablo Torre (2). Barcelona shrugged off their injury crisis, their tiredness having played -- and been beaten -- with ten men at AS Monaco in the Champions League on Thursday, plus the juvenile nature of their XI (never mind the fact that Villarreal attacked them with venom and could themselves have scored five or six times) yet won in stunning fashion.

In the short time since joining, Flick has put huge faith in a raft of junior and completely inexperienced players from his youth system and produced winning, high-scoring, top-of-the-league football, which makes him, if you pardon the comparison, Barcelona's version of David Blaine or David Copperfield.

The reason he urgently needs to top those feats and conjure up something even more special is the horrible injury to his first-choice goalkeeper Marc-André ter Stegen.

The Germany international had made three fantastic saves to keep rampant Villarreal at bay before collapsing in agony when clutching a cross just before half-time. Barça announced that the 32-year-old suffered a "complete rupture" of the patellar tendon in his right knee, and sources have told ESPN that he will be sidelined for months and is unlikely to play again this season.

The crux of the matter is that Ter Stegen's deputy, Iñaki Peña, is simply not good enough to help the Spanish Liga leaders maintain their extraordinary progress, and definitely not good enough to help Barcelona achieve the top-eight status required in order to progress automatically to the Champions League knockout rounds. No need to go into depth about Barcelona's financial fair play (FFP) problems, or their 1 billion global debt, the harsh truth is that it's essential Barcelona progress in the Champions League and grasp the revenue that can begin to free them from their damaging financial restrictions -- or else the vicious cycle continues.

If I sound mean about a 25-year-old who managed to see out the victory against the Yellow Submarine on Sunday, then let me remind you of the horrors that Barcelona suffered when Peña deputised for Ter Stegen last season. Statistics don't tell the entire story, but they are a good beginning.

Peña played 17 times across four competitions for Xavi Hernandez's side and conceded 32 times. Is a goalkeeper responsible for every ball that flies past him? No, but when you are shipping in such high numbers, and then there's a stark comparison when Ter Stegen returns to the side, the evidence builds. (The German only conceded 27 in 28 LaLiga matches last season.)

Peña also played his part in some of the landmark humiliations that contributed to Xavi's eventual dismissal: 3-2 against Royal Antwerp, 4-2 at home to Girona, 4-1 against Real Madrid in the Spanish Supercopa final, a 4-2 Copa del Rey elimination at Athletic Club, 5-3 at home to Villarreal. See the pattern?

This is not, by any means, an attack on the keeper. It's the same cold-eyed analysis that Flick and his staff will have been carrying out from the beginning of their 162-mile journey home on Sunday night.

Is Peña the answer to Ter Stegen's absence? That's where Flick's next magic trick needs to be his most impressive piece of conjuring yet.

By the time Ter Stegen returned from back problems last season, it was obvious that his Spanish deputy was relieved to be out of the firing line.

Peña, by modern standards, is a relatively small keeper whose worth is based upon agility and old-school save-making. Where he is not excellent is in either his distribution of the ball from his feet or when he is asked to be the "free man" sweeper at the back, when Barcelona play out by beating their opponents' press. While Peña was in the team, Barcelona's rivals quickly understood that if they harassed, hurried and pressed him, he would likely hand possession back or make an error.

Has Peña assimilated this experience and benefited from it? Has he gone back and looked at the tapes, learned from his mistakes and become a stronger, better resource for his club?

Remember, in Spanish football, the backup goalkeeper doesn't get to play for the B team. His only work is in training; there is very little opportunity to apply the lessons learned from that extremely bruising and bumpy spell when he was in pole position.

Flick and his numerous staff are still very new to the club -- don't forget that. They have been able to see Peña in training since late July, that's true, but none of them have been first-hand witnesses to how he reacts under the spotlight or shoulders the immense pressure that a Barcelona side using a very high defensive line places on any goalkeeper.

Back to the requirement for Flick to produce some magic.

Can he, and his staff, mentor Peña and ensure that he competently sees them through to the next transfer window at least? I will declare my colours now: I don't think a decision to stick with the No. 2 and continued trophy challenges are compatible.

Were it not for those pesky FFP regulations that, remember, meant that Dani Olmo couldn't be registered for the first part of the season once he signed from RB Leipzig, then the club would have brought in a goalkeeper to ensure that this sort of situation would never occur in the first place. They were simply too financially restricted to even contemplate that, though.

They set sail into the new Flick era with fingers, and everything else, crossed that their German captain wouldn't be injured. Now, lo and behold, disaster.

Flick has options.

He has been ultra daring (and successful) in how much faith to place place in a stream of young players with no previous impact on the first team. So, could he reach into the youth ranks and select someone who vaults over Peña yet helps maintain this run of games in which Barcelona have won six out of six and scored 22 times in the process?

The first option is 20-year-old Ander Astralaga, who, while he often sits on the first-team bench, is, nevertheless, the Barcelona B goalkeeper. The Basque is patently talented, confident and has racked up decent experience in the youth ranks, but he is a little impetuous and known for still having a few too many errors in his game.

Budapest-born Áron Yaakobishvili is rated behind Astralaga so shouldn't, in theory, be ready to supplant Peña. The Miami-born golden gloves of the youth system, 18-year-old Diego Kochen, who's the best of the lot, has a hamstring problem that is scheduled to keep him out for nearly a month.

The rules on Barcelona acquiring a new goalkeeper, outside the transfer market, are crystal clear -- and only moderately helpful. If Ter Stegen is medically certified to be out for more than four months, then Barcelona will be permitted to seek a replacement, but there are strict parameters.

Any goalkeeper they choose would not only have to be out of contract but not registered with any club when the summer transfer market ended, meaning that if a keeper who was unhappy at his present club was suddenly released from his contract, he would not be eligible to immediately play for Barcelona. Them's the rules.

Nevertheless, there are candidates: Keylor Navas, Edgar Badia, Jordi Masip, Tomás Vaclík. This list brings us right back to the need for Flick and his assistants to not only produce a magical solution but to get things right, under pressure, before their remarkable momentum in LaLiga is upset.

The games come thick and fast, against Getafe on Wednesday, away to Osasuna this weekend and then a crucial Champions League fixture against Young Boys of Switzerland next Tuesday. They need time to think and breathe, but there's no time -- except time for a little bit of Flick magic.