It seems to be a recurring theme in Pompey's recent performances where there is a marked improvement after the break following a below-par first 45 minutes.
And Pompey were made to pay for that today following some sloppy defending having been let off the hook on more than one occasion.
The defence were cut open too many times with Jamie Ashdown first having to make a double save from James Henry and Jason Puncheon, though the Southampton loanee was offside.
But the biggest let-off came when Millwall again cut through Pompey on the right hand side and Liam Trotter's shot hit the post, with the ball breaking to Henry who somehow put the rebound wide.
Trotter would find himself on the scoresheet soon after though after Ashdown could only parry Alan Dunne's shot up to the head of the former Ipswich man who made no mistake of heading the ball into the net.
On another day Trotter may have had a hat-trick as somehow he couldn't slot the ball in from two yards when yet again a cross came in from Pompey's left side.
The offside flag was raised much to Trotter's relief but the move highlighted Pompey's brittle defence. Steve Morison could have also bagged himself a goal when he raced through on goal, only for a hesitant Ashdown to eventually come out and stop his shot.
The first half was not without chances for Pompey, the best falling to John Utaka who was one-on-one with 'keeper David Forde but had his effort saved.
Liam Lawrence also whipped in a couple of excellent crosses that should have been converted into goals but in honesty, Pompey were slightly fortunate to go into the break at half-time only one goal down.
I don't know what Steve Cotterill says in his half-time team talks but it always seems to work. Pompey came out in the second half with purpose and Brown's shot was cleared off the line right from the restart.
Nugent then slotted in what he thought was an equaliser from two yards only to be denied by a very dubious offside decision as it seemed like the ball may have come to him from a touch from a Millwall player.
Pompey continued to dominate possession and Dave Kitson really should have given Pompey the lead when he turned Tony Craig in the box but could only poke the ball wide. In hindsight, he should have gone down when Craig was pulling his shirt as he would have certainly had a penalty.
Millwall may have doubled their lead after a scrap in the box led to Brown almost putting the ball into his own net, only for Joel Ward to come to the rescue with a goal line clearance.
That was the visitors' only meaningful attempt in the second half as Hayden Mullins was the next man to go close for the Blues as his effort hit the crossbar after his earlier shot in the half had been "Quashied" over the bar.
The equaliser came when Liam Lawrence attempted a shot from distance which he skewed but Kitson was alert enough to cushion the ball with his head to Nugent who nodded the ball past Forde.
Pompey continues to search for a second goal but were almost punished on the counter-attack, only for Ashdown to produce a superb save to deny Morison.
After that it seemed like only the home team would go on to win the game but nobody in a blue shirt would have a shot at goal and instead over-played the ball which allowed the Millwall players to get back in numbers.
In the end we had to settle for a draw and I'm slightly disappointed by the result from a game I believed we would win.
I'm not sure if starting Hermann Hreidarsson was the right thing to do because his lack of pace was exposed and he was caught out of position on more than one occasion, including when Millwall scored as their player had so much space and time to run and then pick his spot.
Steve Cotterill also has to nail why Pompey can only perform in the second half. That's four games on the trot now where we have played badly in the first period and have been made to pay today and against Doncaster last month.
The match did have some positives to come from it, though. Liam Lawrence played well whilst Joel Ward has matured into a good right back and was probably our man-of-the-match today. Greg Halford certainly isn't sure of getting his place back on Tuesday after Ward's performance today.
It's only two days now before we go to Leeds without Liam Lawrence or Michael Brown. Getting a result there is going to be a tall order and you can be sure the players will have to perform for 90 minutes rather than 45.
Pompey Player Ratings
Jamie Ashdown: 7 - Saves kept Pompey in the game.
Joel Ward: 7 - Has matured into a quality player.
Ricardo Rocha: 6 - Some errors but generally OK.
Aaron Mokoena: 5 - Made too many mistakes.
Hermann Hreidarsson: 4 - Still looks out of sorts, not a good return.
Liam Lawrence: 7 - Provided most of Pompey's creativity.
Michael Brown: 6 - Tenacious as always.
Hayden Mullins: 6 - Did his job as usual.
John Utaka: 5 - Wasteful when he had the ball.
Dave Kitson: 6 - Worked hard but missed a great chance.
David Nugent: 7 - Quiet first half but was very involved in the second.
Substitutes
Darryl Flahavan
Ibrahima Sonko (Rocha 66): 6 - Did OK.
Carl Dickinson (Hreidarsson 66): 6 - Looked good when he came on.
Nadir Ciftci
Kanu (Kitson 90): N/A - No time to make an impact.