The Warriors have not won on the road in the Aviva Premiership since April 2009, but they came back from 37-3 down in the second half to register two bonus points with four tries in the last 16 minutes in a 37-31 defeat.
For an hour Northampton dominated with five tries - two from Luther Burrell and one each from Courtney Lawes, Vasily Artemyev and Mike Haywood - seemingly ending the contest.
But Worcester's bench made a huge impact as replacements Jonny Arr, Josh Matavesi, Josh Drauniniu and Ollie Hayes scored tries, while, with time up, Andy Goode secured the losing bonus point with a retaken conversion because Northampton charged too soon.
Hill said: "The Northampton coaches were very worried next to me. If the clock had gone on for another five minutes I think we would have sneaked that.
"I was thinking it was going to be a difficult week with a big game against London Irish on Friday coming up, but that last 20 minutes has certainly lifted spirits.
"I was annoyed about the first half. We got well and truly beaten, but it was a special second half, we played some good stuff and the passes stuck.
"We put some attacking players on the field that can carve up. Josh Matavesi, Jonny Arr, they all made a good impact.
"We picked a heavy pack to start to stop the Northampton forwards, but clearly that didn't happen, we couldn't cope with their scrum or their lineout.
"Northampton had clearly taken their foot off the pedal, but to come to Northampton and score four tries and score 26 points at Welford Road, that is a good sign. We weren't doing that last year."
Northampton director of rugby Jim Mallinder admitted his side, which has won four out of four to start the Aviva Premiership season in impressive fashion, "relaxed" after running away with the game for an hour.
"We made a few changes and disappointingly they got back in the game," Mallinder said.
"I don't think it was panic (among the coaches), it was frustration that we got away from doing the basics and our defence crumbled.
"We didn't hit touch when we had opportunities and we lost the ball in attack. If you start doing that you are always going to be on the back foot."
"We dominated Worcester for 60 minutes. The positive from that last 20 minutes is that a lot of the players got some good game time.
"Courtney (Lawes) was exhausted at the end, he has not played 80 minutes for months, Luther Burrell as well. It is good for them and if we are to win anything this year we need a squad and we need to get these non-15 players playing well."
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