Hamburg recorded a much needed win by putting three past the worst defence in the league, winning 3-2 thanks to a determined fightback either side of the half.
The Fohlenelf traveled to the Volksparkstadion knowing a win would see them leap above Hertha Berlin into fourth place, while HSV sat just three points above the drop zone heading into Sunday afternoon's game.
The Bundesliga's worst defence were almost caught out in the 13th minute as Josip Drmic of Hamburg found space to shoot on the left side of the box, but Yann Sommer saved well.
That sparked a fierce counter attack that led to the opening goal for the visitors. Quick work got the ball out on the right with Thorgan Hazard, who crossed teasingly where Fabian Johnson was waiting at the far post to poke home goal number five on the Bundesliga season.
It should have been 1-1 in the 18th minute when Granit Xhaka gave away possession on the edge of the box after Sommer passed to him inexplicably. Nicolai Müller brought the ball into the box, but his square ball failed to find any of the teammates queuing up as 'Gladbach got away unscathed.
The Dinosaurs bite back
A minute later Sommer was called into action as a ball directed in behind towards Drmic, but he was thwarted by a great intervention from the 'keeper.
After a relative lull in proceedings it was Hamburg who threatened again eight minutes before the break as a range shot from Aaron Hunt almost wrong-footed Sommer, but he did well to claw the ball behind for a corner.
The break was to be short lived however, as the corner was headed onto the bar by Cleber Reis of HSV, before Martin Hinteregger sliced a Gideon Jung shot into the back of his own net to level the game at 1-1.
Parity was to last all of three minutes and three seconds, as the Dino surged downfield buoyed by their equaliser, and Artjoms Rudnevs got in behind before thundering a low shot under Sommer from the right side of the box to give the hosts a lead.
Drmic had the first major chance of the second half when, in the 53rd minute, he got in behind the defence again but blazed his shot high from close range.
Lewis Holtby had a shot a couple of minutes later that didn't lack power, yet was straight at Sommer.
Borussia were presented with their first real chance of the second half with 68 minutes gone as a ball from the left byline courtesy of Thorgan Hazard found Lars Stindl, but the forward could only send a soft volley at Rene Adler.
Finishing the job
Thorgan Hazard had a chance to level the game at 202 in the 74th minute when Oscar Wendt squared to him in the box, and on the spin all he had to do was find the target with Adler out of the equation, but he rolled the effort wide and the chance went begging.
However any fightback wa short lived as Hamburg sealed all three points with ten minutes left on the clock. A corner from the right side was glanced on by Emir Spahic, and substitute Ilo Ilicevic nodded home from close range to make it 3-1 and keep the points in the Hanseatic city.
A nervy finished was ensured when Raffael scored his ninth of the season, clipping a neat finish over Adler with two minutes left on the clock.
When Branimir Hrgota glanced a header goalwards a minute later, home fans must have had their hearts in their mouths. Thankfully for them it went narrowly wide of the far left post.
Hamburg were able to see out the rest of the game and move 11th with the win, sitting on 26 points from 21 games, while Gladbach fail to move fourth, instead staying 7th with 32 points.