There is soooo much more to sex then, well the sex part.
Your man became to fixated on what your partner was doing for you rather then what he could be doing for his partner. Work other areas of the body, make the playfriend feel good in other ways. I for one loved to be kissed and carressed all over, with attention paid to one particular area.......my baby finger, what the heck do you think I ment. *Sick people*
If the woman is treated right, she most likely wont get upset about your SO not being able to "perform". That could lead to another meeting which could then lead to a comfort level for your SO.
Don't focus on the bad, life is WAY to short for that sort of thing.
Your friend,
Prettylady