Despite leading for the majority of the first half, Thunder were let down by poor shooting in the third and fourth quarters as they sank just eight of 40 attempts from the field in the second half.
The hosts did try to stage a late fightback but it was to no avail and Northumbria will now travel to Reading Rockets, who won 80-71 at Lancashire Spinners, in the semi-finals.
Hildreth said: “Obviously gutted to lose in a quarter-final.
“I felt we played well enough in the first half to be in control of the game at both ends. After the break, we came out flat and it set the tone for the remainder of the game.
“Despite playing solid defence, it was our shooting that let us down. We went eight for 40 in the second half, missed eight free throws and shot 11 per cent from behind the arc. Unfortunately, you just can’t shoot that bad and win at this level.”
Thunder, who play their National Cup final against Manchester Magic later this month, had qualified for the last eight of the Trophy in second place in the South Group.
They won four of their six group games – the same win/loss record as Team Northumbria, who finished third in the North Group.
The hosts got off to a solid start against a well-drilled Team Northumbria side and had a deserved 25-22 lead after the opening ten minutes.
Worthing’s advantage then grew in the second quarter and they went into the break with a 48-39 lead.
But then Thunder’s problems began as the side from Newcastle fought back to take a 62-59 lead going into the fourth quarter and ultimately held on to book their place in the semi-finals.
James Cambronne led Thunder with 25 points and 12 rebounds, supported by 13 points each from Tom Ward and Brendan Okoronkwo, with the latter pulling down ten rebounds.
Thunder are on the road for two National League Division 1 matches this weekend. They travel to Leicestershire Warriors on Saturday (3pm), before they head to Reading on Sunday (5pm).
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