Ryan Taylor rescued a point for Pompey against Mansfield today.
It was the introduction of subtitute David Connolly, along with Jake Jervis, which changed an increasingly turgid clash after a bright opening from Pompey.
It is now one defeat in five but also just one win in 14 for the Blues, who remain two points off the League Two drop zone.
Pompey handed a debut to Wes Fogden following his arrival from Bournemouth this week, with a place on the bench for Jervis.
It was a high-tempo start for the home side, but James Jennings was the first to threaten for the visitors as he whipped a 25-yard free-kick just wide after three minutes.
Taylor nearly gave Pompey the lead five minutes later as he flicked Jed Wallace’s free-kick just over.
Mansfield again threatened from a set-piece after 15 minutes when skipper John Dempster headed a corner wide.
The best chance of the half fell to Patrick Agyemang after 27 minutes when he was teed up by Wallace, but he dallied long enough to allow Jennings to block his effort from six yards.
Taylor fired just over from 30 yards nine minutes before the break, but the early energy of the game had dissipated as the interval arrived.
It was Mansfield who upped it after the break and took the lead after 50 minutes.
Darryl Westlake’s cross was headed back across goal by Jennings for Stevenson to acrobatically volley home.
Pompey had completely lost their way, with Ross Dyer and Chris Clements having chances for a second for the visitors.
But a double change from Barker changed the face of the game with 22 minutes left.
The introduction of Jervis and particularly Connolly invigorated the Blues.
Connolly cracked the post with 13 minutes left from 20 yards.
He then freed Taylor with a lovely ball which he angled home 60 seconds later.
It was one-way traffic from there as Pompey launched a late onslaught.
Agyemang had a complete air shot when free a couple of yards out from Nicky Shorey’s corner.
And Jervis had shouts for a penalty ignored as he went to ground from a Ryan Tafazolli tackle late on.
But it was a point Pompey had to settle for despite their late pressure.