Dani Alves scored his first goal since returning to Barcelona, but the Brazilian spoiled his afternoon by picking up a straight red card against Atletico Madrid.
The Brazilian was enjoying a dream day for the first hour, providing an assist for Jordi Alba's first half goal and finding the net himself early in the second half as he responded to being left out of Xavi's Europa League squad.
However, a needless decision to plunge his studs into the back of Yannick Carrasco's leg saw the veteran shown a straight red by referee Jesus Gil Manzano after the official consulted VAR.
Alves' involvement threatened to overshadow debuts for recent signings Adama Traore and Pierre-Emerick Aubameyang, both of whom were involved for Xavi's team in a game full of talking points.
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Barcelona wasted no time handing Traore his second debut at the club, though fellow new arrival Aubameyang was made to wait for his first minutes at Camp Nou.
Spanish international Traore started his career with the Catalan club, and was thrown right in at the deep end for a game which could have a huge bearing on Barca's hopes of Champions League qualification.
Champions Atleti took an early lead through Yannick Carrasco, but Xavi's hosts hit back with three goals of their own before the break - including a Gavi header from Traore's cross.
Traore, a graduate of Barcelona's La Masia academy, came in for some criticism for his perceived lack of end-product at Molineux and elsewhere in England..
His return of eight goals and 14 assists in 160 Premier League games - 123 of them for Wolves - doesn't tell the entire story, though, with Spurs joining Barca in seeing enough from the 26-year-old to launch a January bid.
And, after Jordi Alba had drawn the hosts level with a stunning volley, it was Traore who lifted the ball into the box from the right touchline for Gavi to head beyond Jan Oblak.
Ronald Araujo further extended the lead before half-time, and when Alves drilled home Barcelona's fourth - his first goal since returning to the club - attention turned to the second new arrival.
When Aubameyang took to the field shortly after the hour mark, it was in place of his fellow debutant Traore.
It was 4-2 by then, though, with Luis Suarez turning Jose Gimenez's header beyond Marc-Andre ter Stegen to net against his former club.
There were still 20 minutes left on the clock when Alves saw red, with Gil sticking with his decision despite protests from other Barca players.
It was only Alves' fifth game for Barcelona since returning to the club from Sao Paulo, and his second in La Liga.
There was no faulting the energy and enthusiasm from the 38-year-old, who began his first Barcelona spell back in 2008 and won three Champions League titles with the club.
He wasn't the only person to be shown a red card, though, with a member of Barca's coaching staff sent to the stands for his reaction when Ferran Torres was denied a second-half penalty.
Xavi also went into the book himself, but the 10-man hosts held out for victory despite Atletico putting the pressure on as the clock ran down.
The result was enough to lift Barcelona above Atletico Madrid and into the top four for the first time since August.
Neither side is assured of Champions League football next season, though, and Barcelona will be preparing for life without Alves as he serves his suspension.
