Boyd saw his side go down to a 35-20 defeat at Mattioli Woods Welford Road on Friday night, meaning Leicester have done the double over Saints for the first time since the 2016/17 season.
Tigers trounced the black, green and gold 55-26 at cinch Stadium at Franklin's Gardens back in October and they are currently well clear at the top of the Gallagher Premiership.
Saints are still on the coat tails of the top four, but the second successive defeat to Tigers hurt those of a Northampton persuasion.
"I remember last time when we got beaten very comfortably on the scoreline (in October), we picked it apart and there were a couple of moments in it that were very significant," Boyd said.
"If I'm honest, and I'm bound to say this, I think both scorelines flattered Leicester.
"We're really disappointed to lose for the second time in a season to Tigers. That hasn't happened for a few years.
"We're disappointed with the outcome and disappointed with quite a few parts of the performance.
"It's disappointment all round.
"In the last 15 or 20 minutes of the first half, when it loosened up, we managed to score a try and were perhaps unlucky not to get a second one. It was a good bit of defence from them.
"We were under pressure from them physically, we were under pressure from our decision making and we tried to overplay.
"We were under pressure from the referee's whistle, which all came from various parts of pressure.
"The discipline came from the fact we weren't getting our way in the physical battles.
"When you're getting dominated like that, those breakdowns become very much harder when you're on the back foot.
"Twice the ball hit one of their guys and they got away on us.
"It was a little bit that we didn't get much luck but at the end of the day, you earn and deserve your luck."