However, with Sexton returning from France next season the competition for a starting fly-half berth is set to be fierce.
And Madigan says he has no qualms about changing his role to accommodate the return of one of the game's finest players.
"I've made it very clear that outhalf is my preferred position but I think in sport the posts are always moving," he told the Irish Times.
"For me, with Johnny coming back, I'm not going to be naive.
"He's one of the best players in the world, you're not going to have someone of his ability on the bench so I've got to look at where else I can fit into the team and this year I've been playing a lot at 12 and I've been really enjoying it.
"It is without doubt my most enjoyable season so far and, with Johnny coming back next year, I'd ideally like to play at 12 alongside him."
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