Enrique acted decisively at the interval after watching his starting side struggle to contain the hosts' counter-attacking threat during a difficult opening 45 minutes.
Reflecting on the defensive challenges and the crucial impact made by his substitutes, the Spanish manager explained: "Today was more difficult than usual. In the first half, there were situations we weren't able to control.
"Rennes launched some top-class counter-attacks, and they managed to score two goals with great precision. It was very complicated, very difficult. We tried to make some changes, and I'm particularly pleased with the five players who came on during the match. They all did a very good job."
He added: "The supporters are incredible; whatever our performance, they're always there to support the team. We'd like to thank them and we hope to improve. That's our job, and I hope we can play much better."