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...
5. Conor Shaughnessy - 7
(Replaced by Connor Ogilvie on 62 mins) Great to see him back after more than two months out. Played as left-sided centre-half - 5) - Adds so much class to the Pompey’s defence and it was a strong performance from the Irishman, in terms of defensively and distribution. Wisely withdrawn on the hour mark to protect him. Photo: Graham Hunt
6. Zak Swanson - 8
(Replaced by Jordan Williams on 73 mins) Continues to excel at left-back, raising the question of whether Pompey need to strengthen that part of the pitch after all. Strong, committed and loves a charge down the flank. Photo: Graham Hunt
7. Andre Dozzell - 6
Desperately unlucky to concede the own goal for Arsenal’s leveller. Ploughed through so much work, although continued to use the ball constructively. Photo: Graham Hunt
8. Luke Le Roux - 5
(Replaced by Marlon Pack on 62 mins) Handed successive starts in the centre of midfield and, as ever, was fully committed and didn’t shirk a challenge, earning a second-half booking. Game did pass him by for periods as he attempted to get into the pace of it, yet soldiered on. Photo: Graham Hunt