The 20-year-old started Saturday's 6-1 victory over Alavés at the Spotify Camp Nou, making his first senior appearance for the club after progressing through the youth ranks at La Masia.
It was an especially memorable occasion for the midfielder from Benicarló, who had waited several years for the opportunity to represent the first team in a competitive fixture.
"I'm very happy, very proud after all these years that I have been working. It's every child's dream. In the Primera División, with Barcelona, the club of my life... I'm very happy," Fariñas told the club's media.
His opportunity came in an unfamiliar position, with Flick selecting him at right-back rather than in his customary midfield role. It was a decision that demonstrated the German coach's willingness to trust the versatility of his younger players.
Fariñas had previously occupied the position during pre-season, when he played for almost half an hour in Barcelona's 2-2 draw against Birmingham City in July.
The youngster admitted he initially felt nervous but quickly settled into the contest, helped by the encouragement of those around him.
"I play wherever he puts me. At first I was a little nervous, but then you get into the game and I think I'm a player who has quite a lot of personality. I felt comfortable, to be honest," he said.
The support of his more experienced team-mates was another important factor, particularly with several familiar faces operating around him on the right-hand side.
"They helped me quite a lot. Cubarsí, Rodri, Fermín and Lamine were all there on my side. They gave me confidence," he explained.
Fariñas joined La Masia in 2018 after leaving Villarreal's youth system and has gradually worked his way through Barcelona's development structure.
His debut also represented recognition of the progress he has made, having established himself as an important player for Barça Atlètic during the previous campaign.
For Flick, the performance offered another encouraging example of the depth available from the academy. For Fariñas, however, the immediate priority is to build on a night he will remember for the rest of his career.
The youngster has made his first appearance. Now he wants more opportunities to follow.