United were reduced in number when Kem Izzet lunged in and sent Saints youngster Adam Lallana flying with a scything challenge in the 35th minute, earning himself a red card.
Both sides had chances to win the game but neither found the back of the net, and Boothroyd was pleased with all aspects of his new side's play.
He said: "I thought we defended fantastically and this feels like a win. We were obviously forced to defend for a large part of the game after the sending off, but we also had chances of our own to win the game.
"I thought to a man we were fantastic, so there are plenty of positives from the game. It is just great to be back involved though and I can only see progress for this club."