After being restricted to 132-9 in 50 overs after losing the toss at Havant Park, the hosts bundled Burridge out for just 85.
Spinners Chris Morgan, Chris Stone and new teenage West Australian import Louis Clayton took a combined 7-35 from 21 overs.
Havant had endured a tough close season, losing three top order batters - former captain Ben Walker, Harry Gadd and George Metzer - and seam bowlers Richard Jerry and Waterlooville-bound Sonny Reynolds.
And it appeared an opening-day loss was on the cards after Inayat Ullah (2-11) and Dan Stancliffe (3-28) had reduced them to 21-4. After Stuart Ransley was trapped leg before by Ullah with the score on 15, Clayton was then bowled first ball.
Chris Stone was caught by Matt Goles off Stancliffe, who then bowled Morgan for a duck to leave Havant in some disarray. Captain Hopson, desperate to keep his bails intact, crawled to 24 off 110 balls before he was sixth out with the score on 71.
Feeney and Oli Jones (16) put on 48 for the seventh wicket as Havant ended on 132-9 - extras the second top scorer with 29, including 19 leg-side wides.
Burridge reached 39-1 in reply when Morgan trapped South African Goles, the leading runscorer in the SPL top flight in 2023, leg before.
Clayton’s first league wicket saw him bowl Burridge captain Joe Collings-Wells and it was 66-5 when Morgan dismissed Francis Moore for a duck - having previously having Azimunnoor Chowdhury leg before, also without scoring.
Left-arm spinner Morgan, who had opened the bowling with debutant Aron Tubman, ended with 3-15 from eight overs, while third change Chris Stone (3-7) and Clayton (2-9) also helped spin the champions to a surprise loss.
“The sense of pride around the club on Saturday evening was special. The number of messages of congratulations from the wider cricket community was warmly received.
“Ben and Ollie put on a great partnership of 48 in approximately 10 overs which changed the momentum of the innings at the right time.
“We had endured a tough test early on a wicket that was damp thanks to the heavy rain during the middle of the week. Ben played a range of unique and classy shots, and punished anything short.
“Bowling wise, we did really well. Morgs was particularly brilliant with the new ball. Once he got one to bite off the surface in the third over of his spell, the dynamics changed for the batters.”
Photographs by Martyn White