The American head coach was in no doubt where the game had been lost.
"This isn't how we wanted to start. We lost the match in the first half, that's clear, because we didn't have the intensity, the spirit or the courage that define us and show who we are," Matarazzo said.
"It's the first time this season we haven't started a game well, because normally we start well. In fact, our last defeat came near the end of the match. But this game was different — we started very badly, conceded two goals too easily, and spent the rest of the match chasing the scoreline."
Matarazzo insisted the turnaround after the break, which saw Héctor Fort replaced by Gonçalo Guedes, owed nothing to a change in system.
"In the second half we found ourselves again, that's clear, and we did it without changing anything in terms of structure or game plan. It was the same plan, but what changed completely was the attitude, which was different out on the pitch," he said. "We were a much better team, and with the goal and the chances we created, I think we deserved more than what we took away today."
Pressed again on the poor start, Matarazzo admitted he could not fully explain it.
"I don't know why we started the way we did. I don't know if there was too much respect, a lack of activation or a lack of connection between the players, but we made a lot of errors in our decisions, we lost the duels and the second balls," he said.
"At half-time I told the players it wasn't about what we were doing, but how we were doing it. We needed to play with more courage, with more intensity, and find our identity again — the identity that has brought us our moments of success — and we found that again in the second half."
On the tactical picture, Matarazzo explained the adjustments were more about personnel than structure.
"Fort was defensively prepared for their 1-4-3-3, depending on the height of their left-back he either acted as a winger or dropped into a back five if they pushed higher. The only thing that changed were the profiles in central midfield. We didn't do anything different from usual — we've regularly built with a back three this season, and last season too," he said.