The Giants trailed by just one point at 22-21 in the fourth quarter before a spell of three intercepted throws in the space of nine attempts from quarterback Eli Manning allowed the Philadelphia Eagles to pick up a 36-21 win.
There were also three intentional grounding penalties for the Giants as they fell to 0-5 for the season, and Coughlin puts much of the blame for the latest defeat on the shoulders of two-time Super Bowl MVP Manning.
"Twenty-two to 21, and it's a good football game. We just started the fourth quarter and there's no reason to believe that we can't continue that kind of play. Then the turnovers started to come. That gave them the short field and the easy scores. It was very demoralising for the sideline," Coughlin told reporters.
"I honestly believe that [Manning] is trying so hard to get us a win, he's almost put too much on himself. And I'm not making excuses. There were a couple of those plays that were terrible. The intentional grounding penalties hurt so badly, because not only distance but to lose the down.
"I think we can make some progress with regard to preventing that. I think we do have to sometimes just cover the ball and go down. I just grabbed him a moment in the locker room. He's way, way too good a player to have these kinds of things happen."
Manning now holds the dubious honour of leading the league in interceptions this season, having committed 12 already.