The Catalans claimed a remarkable 5-3 Copa del Rey quarter-final win on Wednesday after forcing extra time at Estadio Nuevo Los Carmenes.
Barca were trailing 2-0 as late as the 87th minute only for Antoine Griezmann and Jordi Alba to force the additional period, after Francisco Trincao, Lionel Messi and Ousmane Dembele had all hit the woodwork.
Griezmann made it 3-2 only for a Fede Vico penalty to level matters again, but Frenkie de Jong scored from a rebound and Alba smashed home a stunning volley to secure Barca's semi-final spot.
Koeman last week suggested his side were not ready to compete for the biggest trophies and the Barca boss remains unconvinced they could end 2020-21 winning LaLiga, the Copa and the Champions League.
However, he believes their fightback against Diego Martinez's side could perhaps be a turning point in their campaign.