Paul Cook suffered a disappointing return to his former club with Wigan Athletic paying a high price for being second best for much of the game at Portsmouth.
The visitors enjoyed their best spell of the game in the first half, creating a few half-decent openings only to fail to make the most of them.
And once Portsmouth took the lead through Brett Pitman’s penalty five minutes before the break, they never looked back.
Jamal Lowe doubled the lead 10 minutes into the second period, and Latics struggled to stem the bleeding before attempting a comeback in the final quarter.
Substitute Will Grigg did pull one back, with a clinical header a minute from time.
But it would have been harsh on the home side had they not managed to hang on for all three points that keeps them in the play-off hunt.
The result - coupled with wins for Blackburn and Shrewsbury - sees Latics slip to third in the League One table.
But with games in hand over both of their promotion rivals, Wigan’s fate still remains in their own hands.
Despite having a day’s less preparation, having played on Easter Saturday, Portsmouth flew out of the blocks.
A cross from the right caused panic in the Latics defence, and it required a great block from Chey Dunkley to deny Pittman a shooting chance.
After finding their feet, Latics created a couple quickfire opportunities which they were unable to take advantage of.
First, Max Power tried his luck from 25 yards, and Luke McKee had to be alert to touch it round the post for a corner.
Then, a Gavin Massey cross rolled only just in front of James Vaughan, and all the way through for a goal-kick.
Latics had a massiev shot for a penalty turned down when Nick Powell fired in a free-kick from 25 yards that was blocked by at least one hand in the Pompey wall.
Referee Tim Robinson waved play on, however, and Latics were further frustrated when Dunkley headed over and Vaughan dragged a shot wide, both after good work from Power.
After soaking up all that Latics had to throw at them, Pompey then broke and took the lead with five minutes of the first half remaining.
Ben Close raced into the Wigan box before being tripped by Dan Burn, and Pitman sent Christian Walton the wrong way from the spot.
It was almost 2-0 within a matter of seconds, a bad mistake by Callum Elder allowing Nathan Thompson in.
Walton this time was able to make the save - much to his team-mate’s relief.
Latics boss Cook elected not to make any changes at the interval, electing instead to give his players the opportunity to dig themselves out of the hole they were in.
Within 10 minutes of the restart, however, the task facing the Wigan players had doubled.
A quality ball into the box was superbly controlled by Lowe, whose cool finish was too good for Walton.
Latics thought they’d found a goal back from a set-piece, but Power’s corner was adjudged to have curled out before swinging back in, before Dunkley’s header back was nodded in by Vaughan.
Latics made a double change at the three-quarter mark, with Grigg and Ryan Colclough taking over from Vaughan and Gavin Massey.
Colclough had a golden opportunity within seconds of his introduction, after Nathan Byrne played him in, but his shot sliced wide via a deflection.
There was even more proof it wasn’t going to be Wigan’s day when Powell advanced on goal and flicked goalwards, only for the home goalkeeper to tip the ball on to that bar and away.
McKee pulled off another great save to deny Grigg, after good work from Byrne and Jacobs.
Gary Roberts took over from Jacobs for the final few minutes, and he provided the cross for Grigg to eventually find the mark with a minute to go.
Sadly there was to be no further sting in the tale, leaving Latics to lick their wounds on the long trip back up north.