This is, they say, the point where the Champions League is to all intents and purposes the old European Champions' Cup once again: straight up, cut-throat, knockout soccer between Europe's best. Leverkusen should have been, then, the perfect environment, for FC Barcelona to begin to carve their place in history that a fair number of the viewing public feels this current side deserves.

Describing Barcelona as the best side ever (or one of the best sides ever) has become a cliche, yet we haven't really reached the point at which that particular accolade can have too much meaning. Giving a team, or indeed any achiever in any field, historical context without chronological distance is quite problematic.

Assessing an achievement years afterwards allows the euphoria of seeing something magical unfold before your eyes to fade, allowing us to consider with sobriety. Distance also makes it harder to see the minor blemishes on the face of an achiever, of course, that may mean little given time.

Those blemishes, at the moment, are Barcelona's away form. The team's scratchy form away from the Camp Nou in recent months appears to have already torpedoed any chances of winning La Liga for a fourth successive year, but this wouldn't be the end of the world were Barça to go on to become the first side to retain the Champions League (since its 1992 reformat) at the Allianz Arena in Munich on May 19.

One can argue that domestic difficulty doesn't necessarily transfer to the Champions League, and that Barça's away form in the group stage proves that. Yet an average of four goals per game away from home in the Champions League is a misleading stat, given that the less-than-mighty BATE Borisov and Viktoria Plzen shared group stage space with the Catalans and Milan. The win at the San Siro was highly entertaining but, in terms of real meaning, must be qualified as little more than a glorified exhibition match played between two already-qualified teams. Milan also played an hour with 10 men after Alberto Aquilani was sent off.

Away struggles in La Liga give a clearer indication of where Barça is at. In a domestic competition that is supposedly a cakewalk for the champion and Real Madrid alike, Barça has managed only two wins in its last eight matches: at Málaga and - bizarrely - in the clásico against Real Madrid. The defending champion has managed only four away wins all season in the championship.

Even the magnificent Lionel Messi has been subject to the malaise. Excluding his sublime hat-trick in that romp at Málaga, Messi has only scored once away - the stoppage-time equalizer at Athletic Bilbao in November - despite having scored 23 in just 22 La Liga games overall. Though hopes of retaining the championship may have been and gone before Saturday's shock defeat by Osasuna, the feeling in the Barça camp was that the loss at the Reyno de Navarra was a failure too far.

Coach Pep Guardiola shirked none of the blame post-match, but he was not the only one with cause for reflection. Accordingly, Gerard Pique didn't even make the bench for the game in Leverkusen. The former Manchester United defender looked relaxed enough wandering around backstage at the BayArena in his tracksuit, but the message from the boss is clear. Refreshment, and refocus, is the order of the day - for everyone.

Guardiola needed no reminding of the potential pitfalls of a visit to Germany. Despite being unbeaten in its previous seven trips, the parallels with the tie against Stuttgart two years ago in the build-up - described as "a difficult moment" by Guardiola in his pre-match press briefing - were lost on nobody. Caricatured as a Champions League choker when it comes to the business end of the competition, Zlatan Ibrahimovic saved Guardiola's men with an equalizer in the first leg at the Mercedes-Benz Arena.

The theory that the last 16 stage onwards represents a return to the traditional format does have one slight flaw. Were that really the case, the likes of Bayer Leverkusen - non-champions at domestic level - wouldn't be in it. Last season's Bundesliga runner-up has been well aware of the size of its task ever since the draw was made back in December. Sporting director Rudi Völler told Sky Germany at the time: "If we play to our best twice and Barcelona has an off-day, then maybe we have a small chance."

The weeks of build-up were unkind to Völler's club, as it lost Sidney Sam through one injury and striker Eren Derdiyok via another (when he stepped on some shards of broken glass when exiting the shower at home). Given his own recent battles with the club's management, the news that Michael Ballack would be unfit for the game after sustaining a minor knock in Sunday's training session was met with relief in some quarters.

The comparison in Champions League experience was stark too. Before kick-off Michael Kadlec had the most Champions League appearances for Leverkusen, with 12 appearances, while Carles Puyol and Xavi had both passed the 100-game mark. Another half-a-dozen of the group have played over 50 Champions League games.

It started out like business as usual. The match was 73 seconds old before Leverkusen so much as touched the ball, and the first German boot on it was on the end of Stefan Reinhartz's outstretched leg as he lunged to cut out Dani Alves' raking pass towards the lurking Messi.

The metronomic possession was present and correct, and Leverkusen was a virtual prisoner in its own half. The demoralizing effect was clear. When goalkeeper Bernd Leno hoofed a clearance downfield, way over the heads of Gonzalo Castro and Renato Augusto, the pair dropped their heads, crestfallen and starving for scraps.

Yet Barça's problems were apparent. Despite the home side gifting Barça the ball straight back on the rare occasions that it managed to win the ball, Leno had very little to do. When Messi was crowded out, there was little apparent in the way of penetration - just as away at Villarreal or Getafe. The one time that Messi was given an inappropriately large patch of breathing space in the center of the field, he lofted through a pass for Alexis Sánchez to slide in the opener.

If the second period showed us a bit more of the verve of the 'real' Barça, it was thanks to this goal, which made Leverkusen chase the game. And chase they did, even if a sparkling display by Messi finally succeeded in deciding the game, and probably the tie.

"In the first half we couldn't make a lot of chances," Javier Mascherano told FOXSoccer.com after the match. "They came at us second half with lots of long balls and crosses; they're much better in these cases, as a physical team, than us." It was a fair admission of how Barça rocked, firstly when Kadlec briefly equalized with Leverkusen's 200th goal in European competition, and then again in the five-minute spell when Augusto forced a sharp save from Victor Valdes and Castro battered the post.

Certainly nobody can say Barça lacks doggedness after persevering on a wet Valentine's night on the industrial Rühr. If half the battle of curing a problem is recognizing it, then Guardiola's men have a start. "We have to improve (away from home) if we're going to succeed (this season)," Mascherano nodded as a parting shot.

The glitter of silverware might define historical achievement, but the less glamorous nights of hard graft are a big part of it - as are the faults and lessons learned along the way.