The Bees twice came from behind before Yoane Wissa beat Bournemouth goalkeeper Kepa for the winner on the hour mark.
Iraola later said, “It's a hard one for us because I'm quite happy with the performance really.
“I think we especially in the first half we were clearly the better team but it's true that we couldn't make the difference.
“You finish 1-1 (at half time) and probably the second half has had less rhythm.
“There have been a lot of things but it has been more stop and go, set plays. Probably a key moment is when we concede after the 2-1."
He also told the Daily Echo: “I think Brentford is a team that plays very well every single second, every single minute and they manage very well every situation.
“I think we've started really focused, winning the second balls, playing a lot in their half and it's not easy to come here and play the way we did the first half.
“I wouldn't say 20 minutes, I would say the first half because I think overall we were having the clear chances and even in the second half probably we made mistakes after scoring and we haven't had this rhythm in the second half of playing, of having this level of football.
“But still there I think we've had the last one, the crossbar is a double header, we don't score. For me, the Evanilson one against the keeper is a clear penalty.
“We don't score but we've had the chances.”
“But more or less the game has been what we expected, similar to the games Brentford has played here at home.
“The throw ins, the kickoff, you have to manage these situations and they punished us there.
“But I think our performance deserves much, much more today.”