Andy Carroll broke Rovers hearts as ten-man Liverpool won 3-2 in a pulsating match at Ewood Park.
The much-maligned centre forward headed an injury-time winner after Rovers had come back from two-goals down to level.
Maxi Rodrigues set Liverpool on their way with two early strikes before goalkeeper Doni was given a straight red for hauling down Junior Hoilett in the area. Substitute 'keeper Brad Jones impressed immediately when he saved Yakubu's penalty, but Yakubu quickly overcame that disappointment when he headed home David Dunn's free-kick.
The second half saw Rovers go in search of an equaliser and when Brad Jones upended Yakubu in the box on the hour mark the Nigerian made no mistake this time, Jones fortunate not to also receive his marching orders.
The final half hour saw Rovers look for a winner but it came at the wrong end when a half-cleared corner was put back into the box where Agger headed on for Carroll to score.
It was a tough end for Rovers to take, they had worked saw hard to get back into the match only to see it snatched from them at the death.
Two changes were made from the Rovers side that lost last time out at West Bromwich Albion. Steve Kean opting to bring back Mauro Formica and Marcus Olsson into the starting eleven with Morten Gamst Pedersen and Jason Lowe dropping to the bench.
For the visitors, they made six changes from the side that drew with Aston Villa on Easter Saturday.
After a cagey opening that saw a Martin Olsson free-kick the only effort towards goal, the game sprang into life with two goals for Liverpool in the space of three minutes.
On 13 minutes a Rovers attack broke down and suddenly as the ball was shifted from left to right the searching ball picked out Craig Bellamy in acres of the space. The former Rover took full advantage, charging into the area before squaring the ball along the six-yard line for Maxi Rodriguez to tap home.
No sooner had Rovers regrouped than they found themselves two goals down. Jonjo Shelvey took up the attack after robbing David Dunn in the centre of the park and as Rovers backed off the young midfielder shot, Paul Robinson couldn't hold his effort and although Bradley Orr blocked Andy Carroll on the follow-up the rebound fell straight into the path of Rodriguez and he made no mistake for his second goal.
Hoilett is brought down by Doni
Approaching the half hour Rovers missed a great opportunity to get back into the match. As Junior Hoilett burst through in on goal he was taken down in the box by Alexander Doni which left referee Andy Taylor little choice but to send the Liverpool goalkeeper off and award a penalty to the home side.
But as Yakubu stepped up to take the resulting penalty kick substitute goalkeeper Brad Jones endeared himself to the Liverpool fans in the Darwen End by diving the right way to comfortably save the Nigerian's effort.
On 36 minutes, ten minutes after his penalty miss, Yakubu redeemed himself by reducing arrears with his 15th league goal of the campaign. After Craig Bellamy had handled, David Dunn floated the resulting free-kick into the area where the Yak rose to head unopposed into the back of the net.
That goal saw Rovers end the first half on top, Grant Hanley was inches away from connecting with a vicious centre from Martin Olsson, whilst David Dunn tested Brad Jones with a long-range strike.
Rovers looked to take advantage of the extra man at the start of the second half but whilst the momentum was with the home side, it was the opposition who had the early opportunities.
The first came on 48 when from a Craig Bellamy corner on the left Andy Carroll escaped the attentions of Scott Dann, but although he connected well with a diving header, the ball went the wrong side of the upright.
Four minutes later and Carroll fed Bellamy as they broke quickly from a Rovers attack, thankfully as the Welshman bore down on goal Grant Hanley got back to clear the danger.
David Dunn and Grant Hanley both saw efforts saved by Brad Jones as Rovers upped the pace, but on the hour mark Liverpool were very fortunate not to be down to nine men.
As Brad Jones went to deal a back pass, his clearance struck the onrushing Yakubu, the ball looped high towards the goal but even so it looked straightforward for the Liverpool 'keeper to claim but he flapped at the ball and as Yakubu stole in the Nigerian was brought down in the six yard box.
Andy Taylor, the referee, blew for a penalty once more, but amazingly he didn't send off Jones, only issuing the Australian a yellow card.
Yakubu took the penalty responsibilities and this time made no mistake, choosing to shoot into the same corner as the first half, this time Jones dived in the opposite direction.
Yakubu scores from the spot
Back on level terms Rovers went looking for the lead, substitute Ruben Rochina very nearly found Junior Hoilett with a ball across the area, before Andy Carroll almost headed into his own net went attempting to head away a Paul Robinson free-kick. The Liverpool striker grateful that Brad Jones was able to tip the ball over the bar.
Grant Hanley headed over Scott Dann's centre, then Rochina saw a shot deflected and saved as the chances came and went.
But as the game entered four minutes of added time it was the visitors who stole all three points.
Daniel Agger had seen his free-kick deflect off the wall for a corner kick, and although Rovers cleared the initial centre by Craig Bellamy the ball was put back into the box where Agger nodded into the path of Andy Carroll and he powered a header beyond the despairing dive of Paul Robinson. It was a contentious goal as Grant Hanley appeared to have been fouled by Martin Skrtel in the build-up, but it went un-noticed by the officials.
It was a desperate way to lose the match after Rovers had worked so hard to get back on level terms, the result still leaves the Lancashire club in the bottom three.
ROVERS: Robinson (c), Orr, Dann, Hanley, Martin Olsson, Formica (sub Rochina 73 mins), Dunn (sub Lowe 75 mins), Nzonzi, Marcus Olsson, Hoilett, Yakubu.
Subs not used: Kean (GK), Givet, Pedersen, Petrovic, Goodwillie.
LIVERPOOL: Doni, Johnson (sub Agger 53 mins), Carroll, Rodriguez (sub Enrique 78 mins), Henderson, Coates, Spearing, Shelvey, Skrtel (c), Flanagan (sub Jones 26 mins), Bellamy.
Subs not used: Aurelio, Suarez, Kuyt, Carragher.
Booked: Orr, Hoilett, Formica, Hanley (Rovers), Flanagan, Rodriguez, Jones, Bellamy, Henderson (Liverpool)
Off: Doni (Liverpool)