The 22-year-old moved to the principality from Valenciennes in the close-season, but had previously been restricted to just 30 minutes of Ligue 1 action, in a 2-0 victory over Rennes in November.
However, with Eric Abidal absent, Isimat-Mirin was given a chance to shine in his side's league clash at Bastia on Saturday, and feels he is more than capable of grasping the opportunity with both hands.
"I knew my time was coming; I had to hold myself in readiness," he told L'Equipe. "I was sure of my qualities.
The French youth international was quick to praise the man for whom he has deputised in recent weeks, remarking: "Abidal is a treat. On the eve of the match, he explains to you already how it will happen.
"Bastia, he was disappointed not to play, but he did share things. When it is for the collective he is still there."
And Isimat-Mirin revealed he was keen to repay the faith shown in him by coach Claudio Ranieri.
"He clearly told me what he expected of me," he added. "He was not wrong. I had to be patient.
"I do what he wants, especially at the tactical level."
