Villarreal trailed 2-0 inside 34 minutes at El Sardinero before goals from Pape Gueye and Nicolas Pépé either side of half-time rescued a point on the Yellow Submarine's LaLiga return, in a game shaped as much by atmosphere as it was by football.
Racing Santander, back in the top flight for the first time in 15 years, raced into the lead through an Andrés Martín penalty in the 20th minute after Comesaña fouled Salinas, before Sergio Martínez doubled the hosts' advantage with a rasping effort from the edge of the area 14 minutes later.
Pérez conceded his side had been swept up by the occasion in the opening exchanges, speaking in his post-match press conference, according to Plaza Deportiva.
"I knew Racing were going to play the way they played. The emotional frequency and the atmosphere could only be what we experienced, which was magnificent after so long. First matchday after promotion, it's an unstoppable emotion. We weren't able to cope with that, and we'll have to see why — whether it's down to tactics or other factors," he said.
"Afterwards we recovered and were dominant with quality, and got two goals. Then there was a spell at the end where the desire to win, the fatigue, the fact it's matchday one, the imprecision of these early fixtures, didn't allow us to make the most of a chance to win it."
Asked specifically about the mix-up that led to Racing's second goal, the Villarreal coach defended his side's approach.
"On the second goal, in a build-up situation, whenever it comes off, you go from one box to the other and create danger, and everyone applauds it. When the opposite happens, you're left exposed on your own with the idea. But it doesn't worry me, especially with Foyth, whose success rate on the decisions he makes is very high. We'll have to look at what happened," Pérez said, before adding of a separate refereeing query: "I've changed teams but my answer is the same."
He was more encouraged by his side's response after falling two goals behind.
"The positive part is the reaction after going 2-0 down. There are always things to salvage, especially in this context. We started the second half well but lacked precision in the final third, and that means you concede the odd transition, as happened," he explained.
Pérez, recalling previous visits to the ground, praised the reception at El Sardinero.
"The atmosphere delighted me, it brings me joy. I played here when Racing were in Segunda B and it was a different atmosphere. Seeing it now is a pleasure for anyone in the stadium."
He also backed Racing's approach under José Alberto López.
"I've seen Racing with the same ideas and style as in recent years in Segunda. In my opinion it's the right call to keep the identity that's brought them success. The first division is a very long campaign and there will be ups and downs. Time will tell whether Villarreal and Racing can get past them."
On a quiet afternoon for Luiz Junior, Pérez offered his support.
"His performance doesn't worry me. When someone has a bad game they tend to be isolated. Luiz had a performance in line with the rest of the team, with some better and some worse decisions. But that's football. How a player connects with supporters often has more to do with what they transmit than their success or error rate. I don't know the context from his time at Villarreal, but he has quality and he's been improving."