James Christian’s men have now won five and lost five of their 10 completed fixtures.
Christian and Duggan entered the fixture as two of the leading eight runscorers across all four divisions of the SPL.
But neither lasted long - both trapped leg before by Yannick De Mezieres Lepervanche as the hosts reached 34-2. Duggan, the second highest run-getter in the SPL, was out for seven while his captain made just one more.
No 3 Will Smitherman top scored with 37, adding 43 for the fifth wicket with Hemanshu Hirani (24). But when Smitherman perished, Hirani immediately followed suit to leave Portsmouth 108-6. And when Matthew Walton (0) lasted just four balls, three wickets had tumbled for no runs.
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Portsmouth were eventually dismissed for 11 with only two players and extras (23) getting into double figures.
Andrew Marston (3-24) reduced Calmore to 34-2, but opener Ben Johns (57 not out) and Shawn Johnson - a 46-ball 50 - put on 93 for the third wicket and the visitors cruised to victory with almost nine overs to spare.
Sarisbury crashed to the bottom of the Division 1 table after losing to previous cellar dwellers Andover.
Rob Franklin crashed a 26-ball 50 - with six fours and two sixes - as Sarisbury, who had chosen to bat, posted 192-7.
Captain Josh Hill (37) and former skipper Ricky Rawlins (31) were the only other two Athletic batsmen to score more than 11, though, and 26 wides contributed to a total of 29 extras.
Opener Sam Ashman (76 not out) underpinned Andover’s reply, batting throughout and hitting the winning run with four balls remaining.
Sam Hill (2-27) and Josh Hill (2-38) were Sarisbury’s chief wicket-takers.
Though they are now bottom, Athletic are by no means cast adrift - third bottom St Cross 2nds (in a position of safety) are only 0.47 of a point average above them with six games remaining.