RUNCORN suffered a third successive only-goal defeat in a Nationwide North match, suspended for three-quarters of an hour by an injury to a Gainsborough player.
Trinity substitute Simon Bird was eventually taken to hospital after suffering a suspected broken leg in a tackle which earned home left-back David Ness a red card.
The incident came four minutes into the second half and furious Runcorn manager Steve Soley was sent to the stands when he became involved in the argument.
After the stoppage, the teams were allowed a warm-up period. Surprisingly, Runcorn played better with 10 men but numbers were evened up in the 76th minute when Gainsborough's Jamie Sherlock used his head in retaliation against home sub Tom Field and was also red-carded.
Runcorn had more penetration with the introduction of striker Tom Taylor whose extra pace troubled the visiting rearguard, while James Lock also showed some drive on his introduction.
But finding the net at home has become a big problem for Runcorn, who are now just one place above the drop zone.
The winning goal had come after just 10 minutes of the marathon encounter, with Lee Ellington forced off after colliding with a post when scoring.
RUNCORN: Thompson, Carragher, Ness, Moore, Robertson, Garrity (Field 64), Parle, Willis, Denny (Taylor 61), Young, McGinn (Lock 78). Subs: McDiarmid, Soley.
GAINSBOROUGH: Holmshaw, Purkiss, Burley, Parker, Pell, Sherlock, Wood (O'Brien 63), Hurst, Ellington (Bird 18, Blythen 50), Hallon, Grant. Subs: Allison, Huckett.