And yet again set-piece problems proved costly, with three goals coming from corners and another involving a quick free-kick in the build up as Arsenal capitalised in style.
Colby Bishop opened the scoring on three minutes after Conor Chaplin’s shot had been saved, but Arsenal soon roared back with an Andre Dozzell own goal following a corner.
Gabriel Martinelli added another, then missed from a few yards and then Noni Madueke missed a penalty in a lively first half which finished 2-1.
However, Arsenal controlled the game after the break, with Martinelli completing his hat-trick, while Harvey Blair and Franco Umeh both went off with fresh injuries.
And here are our Pompey player ratings...
9. Adrian Segecic - 6
(Replaced John Swift on 73 mins) Bright, energetic and excellent at pressing as ever, but didn’t do enough on the ball to really impact the game. Played off the right once more, but there remains an argument he is better in the middle. Photo: Graham Hunt
10. Conor Chaplin - 6
Involved in Pompey’s goal when his shot was saved and Bishop followed up to give Blues an early lead. Forced to come extremely deep looking for the ball, which is perhaps to be expected against Arsenal. Blues need him more in attacking situations, though. Photo: Graham Hunt
11. Harvey Blair - 6
(Replaced by Franco Umeh on 40 mins) Had started so brightly, having an involvement in Pompey’s opener, and was linking up encouragingly with Swanson down the left. Then was forced off with injury, which is becoming a familiar tale of woe for the youngster. Photo: Graham Hunt
12. Colby Bishop - 7
Back from injury with a bang, ending a run of 19 games without a goal. It was the Bishop of old, physically a handful, excellent hold-up play and, of course, back among the goals. Photo: Graham Hunt