The controversial moment that decided Real Madrid's fate at La Cartuja was rehearsed, or at least thought through in advance, according to the Real Betis centre-back.
Bartra told Movistar he advanced into the area as the penalty was struck specifically to be in position to clear any rebound, having sought advice on the encroachment rule from a contact in refereeing.
"A few matchdays ago, I think it was Gayà, who did the little jump, and I asked a referee friend of mine from Segunda B, who's not refereeing anymore, and he told me that if you're there but you're not stepping in..." Bartra said, explaining the reasoning behind his positioning.
It was a risk that could have backfired badly had Mbappé taken even a fraction of a second longer over his run-up.
"I tried today to calculate it as best I could — it's true that if he'd struck it half a second earlier or later, it would have caught me inside the area, but I think in the end... I tried to hold my position with my foot planted and without stepping in, and it worked out for me," Bartra said.
He revealed the same calculated approach applies at the other end of the pitch too.
"I do it in attack as well — I hold my run until the very end so I can arrive, because in the end it's seconds, small details. I remember in the Copa del Rey a couple of years ago, against Sant Andreu, I scored almost by wanting to be there, and in the end, I don't know, defending it that way worked out well for me today."
Goalkeeper Álvaro Valles was the other central figure in the save, and he told Movistar LaLiga he had studied Mbappé's penalty-taking habits in training during the week.
"We worked on it during the week with Toni Doblas. From the moment the match started, I was clear where I was going to dive if he took it. His last ones had gone open," Valles said. "I held out as long as I could and saved it. Beforehand I told him, what luck, a penalty in the last minute, what luck — to try to put him off."
Valles also reflected on what the win meant for a Betis side building momentum at home.
"It was very important to keep showing our strength at home, to compete, to keep picking up points here. We knew a tough opponent was coming. Our aim was to get something from the game," he said. "Once we went ahead, I think we knew how to suffer well. We also had that bit of luck you often need, and it was great work from the team. This belongs to everyone, and congratulations to all my teammates who left everything on the pitch to win it."
On the tension of the closing stages, he added: "Yes, some very emotional, very tense minutes. We know the quality Madrid have going forward. With the scoreline as it was, they piled numbers into the box, and fortunately we were able to get the win over the line and keep a clean sheet, which matters a lot personally and collectively. There's still a lot of the league left to keep improving."