Donaldson sinks plucky Pompey
Hull manager Steve Bruce refused to get carried away despite seeing his side move a step closer to automatic promotion to the Premier League with a 2-1 win over Ipswich.
City's victory at the KC Stadium combined with Watford's 3-2 defeat away to Peterborough leaves Bruce's side six points clear of the third-placed Hornets with four matches to play.
Substitute Robert Koren scored the Hull winner seven minutes from time after Anthony Wordsworth had cancelled out Robbie Brady's penalty.
But Bruce sounded a note of caution ahead of their game with Championship strugglers Wolves at Molineux in midweek, with Dean Saunders' side desperate for points after they lost 3-1 at home to Huddersfield.
"We've given ourselves a wonderful opportunity but you only have to look at the division's results today to realise how crazy it is," said Bruce.
"We're in a fantastic position but that's all it is and we've got another tough game on Tuesday (at Wolves).
"Wolves had a horrible result today and they'll be bang under pressure.
"We've seen before how teams at the bottom have beaten the teams at the top, because the division is so even, but it's a good position to be in.
"We can't get carried away, though. We're within touching distance but we're still got a job to do. We haven't got there yet and we've got to see it through."
Bruce singled out matchwinner Koren for praise after he headed home from close range after getting on the end of a cross from Brady.
"Sometimes Robert has his critics, which I find a bit baffling because he's scored 10 goals from midfield," added Bruce.
"He got a similar number last year and not many can do that from a midfield area.
"He's got his faults like everyone else but he's always capable of scoring a goal and you can't take that away from the kid."
The Shrimpers created a hatful of chances but were unable to find the back of the net, making it five games without win for manager Phil Brown since he succeded Paul Sturrock as manager.
Southend's first good chance came midway through the first half when the unmarked Ryan Leonard nodded Marc Laird's left wing cross straight at Rovers goalkeeper Steve Mildenhall.
Ryan Cresswell then headed a Sean Clohessy's cross just past the right post before Britt Assombalonga and Barry Corr both wasted great chances to open the scoring after the break.
Assombalonga headed another Clohessy cross wide of the right post when he should have done better before Corr sent one past the opposite upright after good work down the left hand side from Anthony Straker.
Freddy Eastwood had a low shot well saved by Mildenhall, who also reacted well to keep out Assombalonga's effort and ensure the game ended goalless.
The Bees' dreams of a top-two finish looked slim thanks to strikes from Pompey pair David Connolly and Shaun Cooper until 22-goal striker Donaldson struck with four minutes remaining.
His late winner came after Bradley Wright-Phillips had scored either side of the break in a hard-fought battle.
Wright-Phillips broke the deadlock after 21 minutes when he lashed home a half-clearance from 12 yards.
But the visitors responded within five minutes, Connolly curling home a beauty from the edge of the box before Cooper gave them a shock lead with a skidding long-range drive that sneaked in at the far post.
The Bees, who ensured a play-off spot with the win, rode their luck against Pompey's packed seven-man rearguard.
Connolly lifted a shot over the crossbar after Jed Wallace's low drive was only parried by Bees goalkeeper Simon Moore as the Londoners repeatedly struggled to make the breakthrough.
Brentford boss Uwe Rosler threw on a third striker in Marcello Trotta in the 74th minute and his deft touch teed-up Wright-Phillips to slide home after a goalmouth melee.
The Bees shattered Pompey's spirited resistance in the dying minutes when Donaldson latched on to a slide-rule Wright-Phillips through ball to chip his shot over goalkeeper Simon Eastwood in a dramatic finale.