Burnley manager Sean Dyche slammed his side's performance after they crashed to a 1-0 home defeat to Huddersfield.
James Vaughan netted the only goal of the game for Town 10 minutes after the interval and Dyche admits the Clarets now face a tough task to make the play-offs after extending their winless run to six matches.
"I'm disappointed more than frustrated. It's a very poor performance, simple as that. Unacceptable," said Dyche.
"I didn't think the effort was lacking but we talk about working hard - we also talk about working smart - and we didn't work smart tonight.
"There were too many players who looked confused with their performance. We came away from the basic principles of what we've been doing."
When quizzed about the possibility of finishing in the top six, Dyche added: "It's out of our hands now, it's in other people's hands.
"The only thing we can assure is we need to improve on that, we need to go hard because there's enough games to make it. But it's a big challenge now because those are the games you have to be winning."
Former Southampton striker Connolly gave Pompey the lead in the 22nd minute with a clever glancing header from a curling Jed Wallace free-kick.
But the home side's hopes of celebrating a first victory since October lasted just five minutes before defender Shaun Williams struck a brilliant equaliser.
Williams controlled Daniel Powell's right-wing cross neatly in his stride before flicking the ball up and unlesahing an unstoppable volley into the top corner from 12 yards.
Dons striker Izale McLeod endured a frustrating return to his old club, passing up a host of good opportunities before being substituted just 15 minutes after half-time.
McLeod could have opened the scoring after just 16 minutes when Pompey defender Ricardo Rocha played a clearance straight to the feet of his old team-mate but the striker blazed wide.
Things got even worse for McLeod at the start of the second half when Powell floated in a delightful cross and he somehow failed to make contact with the ball with an attempted header from six yards.
The Bees player/manager claimed his first goal for the club in the 84th minute, though winger Dani Lopez argued it was he who got the final touch.
Jake Hyde's 10th goal of the season in the 33rd minute had put Barnet ahead to keep the hosts outside of the League Two relegation zone.
Hyde netted a brilliantly-timed header from a fine inswinging Mark Byrne free-kick, with Barnet's killer second coming as Davids burst into the box on the left-hand side and steered a shot past Paul Smith, Lopez making sure it had crossed the line.
Southend had started the brighter, Britt Assombalonga twice off target with shots from inside the box during the opening exchanges.
After the break Southend huffed and puffed, with Barry Corr's drive well blocked by Dale Stephens and strong claims for a penalty after Stephens' handball, only for Davids to settle matters against Paul Sturrock's Shrimpers.
