It was, their coach said afterwards, statistically the best campaign in the club's history, with 50 wins, just six defeats and four draws. And he was right.
Xavi left that summer, but with Lionel Messi at his peak alongside a younger Luis Suarez and Neymar, a trident described by Luis Enrique as "the greatest in football history", Barca looked set to dominate at home and in Europe.
Yet five years on, the Blaugrana have failed to win the Champions League again and even though this season's competition is still not completed due to coronavirus, that record is not good enough.
Instead, Barca fans have had to watch in horror as their fierce rivals Real Madrid went on to claim the trophy for the next three seasons. After Berlin, Barca had cut the gap to five European Cups (and were 5-4 ahead in the modern era). But now Los Blancos lead 13 to five overall.
So where did it all go wrong? Mostly away from home, in truth. Luis Enrique's second season brought a league and cup double, but the team's hopes of retaining the Champions League ended at the quarter-final stage.
Barca began the competition with a 1-1 draw at Roma in the group stage in September 2015, a match which is noteworthy now because it is the last time Suarez scored away from home in Europe.
In the quarter-final tie against Atletico Madrid, Suarez struck twice in a 2-1 win at home, but current team-mate Antoine Griezmann ruined Barca's best-laid plans with both goals in a 2-0 victory (3-2 on aggregate) for the Rojiblancos.
That match at the Vicente Calderon would be Dani Alves' final appearance for Barca in the Champions League as the Brazilian left for Juventus in the summer. And it was the Italian team which ended the Catalans' hopes of European success in 2016-17.
In reality, it looked like their campaign was already over after a 4-0 defeat to Paris Saint-Germain at the Parc des Princes in the last 16, but Barca rallied to produce a sensational comeback in the famous 6-1 win at home in the return three weeks later.
"It was almost like winning the Champions League," Gerard Pique said later. "Maybe better." But once again, Barcelona did not win the Champions League, losing out 3-0 to Juve in the last eight and unable to conjure up another 'remuntada' as the second leg ended 0-0.
It was yet another disaster on the road in Europe and an unhappy finale for Andres Iniesta in the Champions League
But Valverde won a league and cup double and there was hope for better in his second season. Messi vowed to do "everything we can to bring back this special trophy" and after a 3-0 home win against Liverpool in the sides' semi-final first leg, it looked likely.
What happened next is well known: a 4-0 loss at Anfield which was the beginning of the end for Valverde as the Reds advanced instead of Barca and also overtook the Catalans by winning their sixth European Cup.
Valverde obviously takes a large share of the responsibility for what happened in both of those games (his only two European defeats), but the players probably should shoulder some of the blame too – especially for the debacle at Anfield.
This season, with Quique Setien now in charge after replacing Valverde in January, Barca will have another chance.
Ahead of Barca's 1-1 draw at Napoli in the last 16, Messi said he believed Barca could not win the Champions League playing the way they were and the Argentine reiterated those thoughts recently.
The break could therefore be a blessing for Barca as the players will have more time to familiarise themselves with Setien's ideas and with no fans allowed inside the stadiums due to health measures following the pandemic, away fixtures could prove less hostile for the Catalans.
Another Champions League trophy is well overdue for Barca in the era of Messi, probably the greatest player of all time, with Iniesta admitting recently that the Blaugrana should have taken advantage of the Argentine's presence to win at least one more European Cup.
Part of the problem has been the sub-standard replacements for top players, with Xavi, Iniesta, Alves and Neymar all having formed part of Barca's last Champions League-winning side.
On top of that has come a gradual decline under Luis Enrique at first and then Valverde, with the team's trademark style eroded in those years as well.
Setien now has a chance to make himself a hero by leading Leo and this Barca side to the trophy when the competition does resume, but he has been left with a small squad and once again, much of the team's hopes will rest upon Messi.
If this season ends in another European disappointment, much of the focus in next year's elections will surely be focused on how Barca can take advantage of Messi's final years at Camp Nou and win back club football's premier prize.
For a team that looked ready to define an era again after the success under Pep Guardiola between 2008 and 2012, it has already been too long.