Lionel Messi scored a penalty as Ronald Koeman's era as Barcelona boss began with a comfortable La Liga win over Villarreal.
Ansu Fati was the game's outstanding player and scored Barca's first two goals, with a first-time finish from a Jordi Alba ball and then a low drive from Philippe Coutinho's pass.
He won the penalty which Messi scored.
Barca had the game wrapped up by half-time as Pau Torres turned Messi's cross into his own net.
Unai Emery's Villarreal offered little opposition, with their only shot on target coming in the final minute.
Messi is the sixth player to score a goal in 17 different La Liga seasons, joining Real Madrid's Sergio Ramos, who joined that club on Saturday.
It was Messi's first game since trying to leave his only club in the summer.
Messi, 33, submitted a transfer request - claiming he was allowed to leave for free because of a clause in his contract - but Barca said he could not leave for less than 700m euros.
He reluctantly announced he would stay because no team would pay that price, and he did not want to take the club to court.
He started in the centre but played on the right and left in a flexible front line.
He had a total of seven shots in the game, forcing Sergio Asenjo into three saves as well as his penalty goal.
Koeman replaced Quique Setien, who was sacked after Barca failed to win the league and then lost 8-2 to Bayern Munich in the Champions League.
Coutinho, who scored twice in that game for Bayern, was back in Barca's starting line-up after returning from a loan spell.
Summer signings Miralem Pjanic, Francisco Trincao and Pedri all made their debuts in the second half.
'No signs of discontent' - the view from Spain
Spanish football writer Andy West
On a night when Barcelona were attempting to move on from a tumultuous summer and take their first steps towards a brighter future, it felt fitting that Lionel Messi was upstaged by the youngster who looks capable of eventually inheriting his crown as the king of the Nou Camp: Ansu Fati.
The 17 year-old winger was a rare positive in Barca's deeply troubled 2019-20 campaign, and underlined his awesome potential with two superbly taken early goals plus the surging run which led to a penalty for Messi's third.
That doesn't mean Messi did not contribute to this one-sided victory over an atrocious Villarreal. Lining up in the false nine position he last regularly occupied in 2014, the skipper was bright and engaged, showing no signs of the discontent which led to his attempts to quit the club during the summer.
And perhaps that's no surprise, because this was Messi doing what he loves the most: playing football, and doing so for a well-balanced team which gave him plenty of freedom to roam without expecting him to do everything, as has often been the case in recent times.
Much tougher tests will come and the feeble nature of Villarreal's capitulation means it's impossible to draw long-term conclusions, but the start of Messi's reintegration could not have been more comfortable.