Sunderland have struck an early blow in the race for promotion after coming back from a goal down to defeat Pompey 2-1 at the Stadium of Light.
Pompey began the brighter and it was no surprise when they took the lead having threatened as Marcus Harness eventually put the ball into the net following an attack that the Black Cats' defence failed to deal with.
However, the lead didn't last long and when the assistant referee judged the ball crossed the line for a corner when it hadn't, Josh Ellis headed in Grant Leadbitter's delivery that the Pompey players could have learned a lot from on the day as their own set-pieces were woeful.
There was some fortune about Sunderland's eventual winner too as Anton Walkes' clearance bounce off the onrushing Aiden McGeady who then beat Christian Burgess easily before squaring to an unmarked Chris Maguire for a tap in.
The second half didn't produce too many chances as Sunderland did what Sunderland do best and that's protect their lead without ever committing too many men forward.
There were a few big chances when Marquis was played through only to skew his shot well wide. Evans' effort was then blocked by Ozturk and McLoughlin had to stretch to prevent Grant Leadbitter scoring an own goal having diverted Ross McCrorie's cross into his path.
That was as good as it got for the Blues who suffered their second defeat of the season in just three league games. To put that into context it took until December 11th for Pompey to be beaten twice in the league last season and already the knives are beginning to be sharpened.
It's true that Sunderland had some good fortune leading up to both of their goals but whilst some people will moan that the ball didn't go out for the corner before the equaliser, the defending leading up to it was sloppy and Burgess was beaten too easily by Ellis for the header.
And whilst Walkes was a tad unlucky for his clearance to bounce unkindly, Burgess was once again beaten too easily before the cross met an unmarked Maguire who should have been tracked.
That kind of defending will surely have Jackett thinking about a defensive reshuffle. James Bolton, Sean Raggett and even Brandan Haunstrup are waiting to replace those culpable for yesterday's result and as we know, Coventry have some attacking players who will seize upon any errors by the back four.
The most infuriating aspect of yesterday's match was how poor Pompey's set-pieces were. The delivery was simply nowhere near good enough and training on Monday will surely be all about practicing free kicks and corners as they were a far cry from some of the more threatening dead balls seen against Birmingham and Tranmere.
It was sad to see just how poor Ben Close was in yesterday's game as he couldn't get his passing right and didn't pose a threat. Is he able to step up and perform during the big games yet?
There were a couple of positives to come from the defeat. Harness is clearly a quality player and looks like an ample replacement for Jamal Lowe and although Marquis missed an excellent chance, his link-up play will clearly result in goals soon. He just requires some quality service.
Up until the equaliser Pompey were comfortable and looked fluid going forward when the ball was being played into feet rather than the hopeless hoof balls that followed soon after. This new-look Pompey side will still take some time to gel and they were narrowly beaten in what is one of the toughest fixtures on the League One calendar.
But now all of a sudden the pressure's on. Fail to beat Coventry on Tuesday night and already there will be some serious questions asked about this squad and the management that's supposed to be good enough to win this division.
Pompey Player Ratings
Craig MacGillivray: 6 - No chance with either goal.
Anton Walkes: 4 - Looked out of his depth.
Christian Burgess: 4 - Beaten too easily for both goals.
Paul Downing: 6 - The only effective member of the back four.
Lee Brown: 4 - Delivery was terrible and defending not much better.
Ben Close: 5 - Totally anonymous after starting well.
Tom Naylor: 6 - Tidied up when he could.
Marcus Harness: 8 - Scored and always looked dangerous.
Andy Cannon: 5 - Didn't get going.
Ronan Curtis: 5 - Still struggling to find form.
John Marquis: 5 - Wasted his one big chance.
Substitutes
Alex Bass
Sean Raggett
Brandan Haunstrup
Ross McCrorie (Walkes 73): N/A - Decent cameo at right back.
Gareth Evans (Cannon 62): 6 - Added some attacking quality and almost scored.
Ellis Harrison (Curtis 62): 5 - Ineffective.
Brett Pitman