Pompey fell at the first hurdle in the Emirates FA Cup after a narrow defeat to high-flying League Two side Luton at Kenilworth Road.
James Collins grabbed the only goal of the tie right at the end of a first half that the hosts just about shaded.
But the Blues were much better after the break and were unfortunate not draw level on a number of occasions before Nathan Thompson’s late dismissal.
Kenny Jackett made two changes from the side that were beaten by Bradford in the league the previous week.
Kyle Bennett and Dion Donohue both dropped to the bench, with Oliver Hawkins and Brandon Haunstrup restored to the starting line-up.
The first half was a niggly affair, with plenty of fouls to break up the play and little in the way of goalmouth action.
Thompson was shown a yellow card for a late challenge on Alan Sheehan, while the reaction of Collins saw him join the defender in the book.
It was the hosts who were first to threaten when Christian Burgess conceded a foul on the left, but Sheehan’s free-kick was just too high for Collins.
Brett Pitman – still wearing a mask to protect his recently broken nose – had a fierce attempt at the other end and Hatters keeper Marek Stech did well to tip it over the bar.
Stuart O’Keefe then fed Ben Close in the box, with Pelly-Ruddock Mpanzu coming across to make a vital block.
The Luton midfielder was not quite so assured in attack, though, and his tame effort was comfortably held by Luke McGee.
There was a scare when Andrew Shinnie disappeared into the visiting fans after straining to meet a cross on 34 minutes and a sigh of relief when he emerged unscathed.
Hylton then failed to make the most of a decent opportunity by guiding Shinnie’s delivery straight at McGee.
But the hosts did break the deadlock in stoppage-time, as Hylton teed-up Collins to lash a shot into the net.
Half Time: Luton 1 Pompey 0
Pompey fans were fuming just after the restart when Jamal Lowe went to ground right in front of them and Seb Stockbridge declined to give a penalty.
The referee then rubbed salt into the wound by deciding the winger had dived and brandishing a yellow card.
Luton thought they had doubled their advantage when Hylton tapped home Jack Stacey’s low cross at the far post, but the linesman had his flag raised for offside.
Luke Berry then drew a smart stop from McGee, with the ball looping up into the air and landing on the crossbar.
But the woodwork soon came to the Hatters’ rescue, as Stech managed to divert Matt Clarke’s looping header against the bar.
Pompey were suddenly looking dangerous with every attack and when Lowe met Matty Kennedy’s cut-back, his shot had to be hacked from the line by Sheehan.
Pitman then met a long ball forward by Burgess, forcing Stech into action to make a save at his near post.
That was the last bit of action for the Blues skipper, though, as he and Kennedy made way for Conor Chaplin and Bennett just past the hour mark.
And Luton almost caught their opponents out when Haunstrup was caught dithering, only for Shinnie to fire wide with only McGee to beat.
It was the visitors more eager to get forward, however, and when Stech kept out Close’s drilled effort, Chaplin fired the loose ball over.
Pompey were desperately throwing men forward in search of a leveller, only to come up against solid Hatters resistance.
And their task was made even harder when Thompson was dismissed for a second bookable offence following a foul on Collins down the left.
Luton almost wrapped things up on the break, with Olly Lee not quite able to send his shot over McGee.
But the Blues were not prepared to just sit back and only a fine save from Stech stopped Close from finding the bottom corner to secure a replay.
Luton (4-1-3-2): Stech; Stacey, Cuthbert (c), Sheehan, Potts; Mpanzu; O.Lee, Shinnie (Cornick 83), Berry; Hylton, Collins
Goals: Collins 45+1
Booked: Collins, O.Lee
Subs not used: Shea, Justin, Famewo, Gambin, D’Ath, E.Lee
Pompey (4-2-3-1): McGee; Thompson, Burgess, Clarke, Haunstrup; O’Keefe, Close; Lowe, Hawkins, Kennedy (Bennett 62); Pitman (c) (Chaplin 62)
Sent off: Thompson (two yellow cards)
Booked: Lowe, Burgess, O’Keefe
Subs not used: Bass, Donohue, Rose, Evans, Lalkovic
Referee: Seb Stockbridge
Attendance: 5,333 (1,143 Pompey fans)