Hummmm.. I wouldn't say anything to him myself, it could change the whole relationship and drive him away... Mike told me of a lady FRIEND that he buddied around with and he enjoyed having a lady buddie. One night she confessed that she was very attracted to him and would like a relationship with him.. After that, he avoided her because it made him very uncomfortable.

Tell your friend to lay low and see if HE shows any interest in her on down the road.