The Catalans led 2-0 at half time in what was a must-win game to keep their LaLiga Santander title chances alive. They were pegged back at 2-2 before leading again, only to then let that lead slip as well to draw.
"Coaches are always questioned," Koeman said after the game. "But I understand that, after that second half, there are questions.
"We are disappointed and we're wondering what happened. We have to move on and prepare for next season.
"As a coach, you're always responsible. We spoke at half time about improving defensively and not dropping our intensity. We were hopeful, we were 2-0 ahead. You don't expect to draw from there."