Leicester delivered a hugely physical display that saw them run out winners at Mattioli Woods Welford Road on Saturday afternoon.
Saints struggled at the breakdown and in the scrum during the first half, regularly finding themselves on the wrong side of referee Karl Dickson.
Dowson’s men were reduced to 13 men in the second period following yellow cards for Sam Matavesi and Ethan Waller, though they did briefly threaten a fightback.
George Furbank scored to make it 19-10 and Tommy Freeman then appeared to have reduced the deficit further with a second Saints try, however Dickson had blown his whistle before the ball was grounded.
It meant there was no review, despite the fact the offence Dickson penalised Saints for – a Henry Pollock knock-on – was not entirely evident.
Tigers won a penalty at the resulting scrum and pushed on to score again following a quick tap penalty from Hanro Liebenberg.
And though Matavesi scored from the final play of the game, Saints left the home of their local rivals with nothing but regrets.
"I've got lots of takes on that game,” Dowson said.
"Breakdown we didn't deal with in the first half. Discipline in the second half, going down to 13 men, giving 23 penalties away to their 11 makes it very tricky to get a result.
"We couldn't quite get in the game. We didn't do three things back-to-back well.
"We were scrapping away and the score at half-time was 9-3 so playing poorly, we were right in the game.
"But around about 50 minutes, it got away from us.
"That penalty count gives them all the pressure and field position and puts us under some heat.
"In terms of our attacking game, we couldn't get going forward for long enough to put them under some pressure.
"That anticipation at the breakdown wasn't good enough and we gave (Tommy) Reffell and (Jasper) Wiese time to get over the ball.
"In the first 20 minutes, we didn't get an opportunity in their 22 because we didn't field the high ball well enough and when we did get an opportunity we lost the lineout.
"There were lots of little things that didn't go our way but we showed great character in terms of dealing with those setbacks because we weren't playing well but we were actually still in it.
"In the second half, you get two yellow cards and you're fighting an uphill battle after that.”
On the decision to rule out Freeman’s score, Dowson said: "It was very hard to see and the referee's made a decision on that. I don't think it would be the thing I was most frustrated about.
"On 51 minutes, when it was 12-3, Liebenberg was sat in the middle of a breakdown and the referee’s done us for holding him in. I was very surprised at that and that then led to 10 metres for dissent and we ended up in our corner, which was when we lost the two players to yellow cards. Those decisions are the frustrating ones.
"If he (Pollock) touched it or he didn’t touch it, the camera angles aren’t accurate enough and I can’t tell so that’s one of those things, but if someone’s sat in the middle of your breakdown and we get penalised for that, it is tough.”