La Roja missed out on top spot in Group E after a shock defeat to the Samurai Blue, but still qualified after Germany beat Costa Rica elsewhere at Qatar 2022.
Having been firm favourites to top the pile and secure a more favourable knockout round tie, Luis Enrique's side will instead face Morocco after its own surprise campaign.
But with no safety net now going forward, Pedri says Spain are more than aware that there will be no second chances after suffering the unexpected defeat.
"We have realised all matches or life and death," he said. "The last game was a tough match. It was a hard blow – we didn't expect that result against Japan.
"Luckily, we have another opportunity. But if we go missing for 10 minutes, if you disconnect, you go home. If they score, it can be the only one they need."
At one point during its final Group E game, Spain looked set to miss out on the knockouts entirely, with Costa Rica instead set to go through as it led Germany.
Pedri revealed he was not able to focus on matters elsewhere after he discovered La Roja could be going out, instead attempting to ensure Spain turned their game around instead.
"I was looking at the scoreboard," he said. "When I saw Costa Rica were second, and we were out, I was trying to look for the goal.
"I didn't realise Germany had took the lead, and we were second again. I was in anguish throughout the game."