Alexis struck from the penalty spot and he scored the first of Sevilla's four goals in their 4-1 win on Sunday.
At 36 years and 290 days old, he is the oldest former player to score against Barça in a LaLiga match and he said afterwards, "They told me we haven't won here (against Barca) in ten years - and that's a long time.
"These things happen in football, and you see how people are away from home. I take my hat off to my teammates. If there was a moment, it was this one."
Alexis also said: "We haven't won in many matches. I've been here for a month and I'm happy. I'm used to breaking records at all the clubs I've been at, and when the crowd is over, you see how the players and the ones on the bench celebrate, and it's beautiful to see.
"I've always had the chance to celebrate, and I've never experienced it sitting down. Sometimes I just sit down to enjoy that beautiful moment."
Alexis would later be questioned in the mixed zone about his effusive celebration after scoring against his former team.
"I had said I wouldn't celebrate, but sometimes anxiety gets in the way. Or desire. It got away from me. The truth is, I have a huge affection for Barcelona," he told gathered reporters.