Pompey were victims of an Emirates FA Cup upset after losing to National League leaders Chesterfield in the first round.
Former Fratton skipper Tom Naylor headed home the only goal of the game in the first half at the SMH Group Stadium.
The visitors had plenty of possession throughout the afternoon, but rarely troubled Harry Tyrer between the sticks.
John Mousinho stuck with the same side that fought from behind to win in the league at Reading the previous weekend.
There were a couple of familiar faces in the opposition line-up – managed by Paul Cook and coached by Gary Roberts – with Naylor and Michael Jacobs starting.
Both sides were looking to play the ball on the floor, but it was the higher ranked visitors who dominated possession in the first half.
And they had an early chance to break the deadlock, with Terry Devlin cutting the ball back for Paddy Lane to hit a shot that was deflected over.
Their opponents soon had an opportunity of their own after Will Grigg had nudged Regan Poole off the ball and squared for Ollie Banks to draw a save from Will Norris.
But the Pompey defender was left in clear pain on the ground, eventually limping off to be replaced by Sean Raggett.
Banks then had another attempt, this time curling the ball past the post after being teed-up by Jacobs.
There was plenty of neat, patient play at the other end of the pitch, although the Blues were struggling to make an impact in the final third.
One surge forward ended with Lane trying to angle the ball home and being denied by a smart Tyrer stop.
But it was the Spireites who did forge ahead on 32 minutes, as Naylor emphatically converted a Liam Mandeville free-kick.
Pompey tried to hit back before the break and there was an opening when Tino Anjorin swung the ball into the box and Colby Bishop’s downward header was kept out by Tyrer.
But Anjorin would not finish the half, becoming another injury victim and his place on the left was taken up by Gavin Whyte.
Half Time: Chesterfield 1 Pompey 0
There was a third change for the visitors at the break, with Zak Swanson replacing Joe Rafferty at right-back.
Pompey immediately set about trying to attack their opponents, but the Spireites looked dangerous themselves.
There was one attempt from Jacobs that was deflected over and another by Banks that flew straight into the arms of Norris.
Things were still not quite clicking for the Blues and Mousinho responded with a couple of attacking switches.
Abu Kamara and Kusini Yengi were brought on with an hour played, as Jack Sparkes and Devlin made way.
It was Chesterfield still looking the more likely side to score again, though, and they might have done if Armando Dobra had not slipped when in a great shooting position inside the box.
Pompey kept plugging away and Lane’s cross found Kamara in space on 67 minutes, but the stooping substitute could only nod wide.
They were still lacking rhythm, however, and when Conor Shaughnessy lost possession, Ryan Colclough probably should have done better than fire into the side netting.
And Chesterfield saw out the closing stages in relatively comfortable fashion to book their spot in round two.
Chesterfield (4-2-3-1): Tyrer; Mandeville (Sheckleford 81), Palmer, Grimes (c), Horton (Freckleton 71); Naylor, Oldaker (Berry 81); Jacobs, Banks (Colclough 64), Dobra (Jones 71); Grigg
Goals: Naylor 32
Booked: Naylor, Jones, Palmer
Subs not used: Boot, King, Cook, Curtis
Pompey (4-2-3-1): Norris; Rafferty (Swanson 46), Poole (Raggett 11), Shaughnessy, Sparkes (Kamara 60); Robertson, Morrell (c); Lane, Devlin (Yengi 60), Anjorin (Whyte 44); Bishop
Booked: Rafferty, Kamara
Subs not used: Schofield, Towler, Stevenson, Saydee
Referee: Will Finnie
Attendance: 8,377 (1,566 Pompey fans)