The mysterious deaths of three friends found in a pal’s backyard hours after watching a Kansas City Chiefs game has left loved ones with more questions than answers. A doctor said it is not outside the realm of possibility they had ingested a dangerous combination of opioid-like substances and alcohol that was “either intentionally or unintentionally” exposed to the trio, RadarOnline.com has learned. Police found David Harrington, 37, Clayton McGeeney, 36, and Ricky Johnson, 38, frozen on the back porch of their pal Jordan Willis’ Northland residence on Jan. 9 after McGeeney’s fiancée requeste…