Stuart Lancaster said France coach Philippe Saint-Andre's decisions cost France the game at Twickenham.
France fly-half Francois Trinh-Duc had been hugely impressive but Saint-Andre took him off on 52 minutes and replaced him with the notoriously flaky Frederic Michalak.
Just a couple of minutes later Manu Tuilagi scored England's try and the hosts went on to win the game 23-13.
And England coach Lancaster said the exit of Trinh-Duc was the turning point of a game.
He said: "I thought we gained ascendancy at that point. As a coach you focus on your own substitutions but you cast a glance at the ones they are making.
"I thought it played into our hands. Our defence just got stronger."
Despite France's poor showing with three straight losses in this year's Six Nations, Lancaster admitted they had given England a thorough questioning.
"It was a proper Test match - that wasn't the France team that played a couple of weeks ago they caused a lot of problems in a lot of areas.
"It was hard work and it took us 65/70 minutes to do it."
Tuilagi had a bruising afternoon, suffering cuts which needed bandages around his head. "I'm very relieved - it was a tough game, the French played really well," he said.
"For us we just focus on ourselves and try and keep the energy, keep playing and break them down."