Likely there's a way to do what you want. Would you be able to post a packaged workbook containing what you're working with? This should speed up the ability to get a quality answer because it would prevent folks from having to recreate what they think you might have set up.
Thanks for pointing that out. I have now attached the packaged workbook.
Once you have Opponents on the Level of Detail shelf, right click on the Opponents pill and change it from a Dimension to an Attribute. This will switch back to the line chart you were viewing before adding Opponents to the LoD shelf, and you can then add the field to your tooltip to get it to show up there.
Hope this helps,
Many thanks for your answer and knowledge!.
That's cracked it.