The Cobblers took an early lead through Scott McGleish's opener at Elland Road on Friday night, but quickly found themselves on the back foot when Giles Coke was dismissed and skipper Chris Doig was forced off with a hamstring injury.
"I was very proud of my players. We were down to ten men against a fantastic Leeds team and the harder we worked the luckier we got," said Gray.
"It was backs-to-the-wall after the sending off. Giles Coke had to go because it was a tug on Fabian Delph. Maybe an older referee might have given him a warning so early in the game, but I have no problems with the decision.
"We are going well at Sixfields so we fear nobody there, though our squad is getting thinner with injuries."