As in the first leg, settled by Joe Cole's goal, it was the home side that enjoyed the better chances, but a penalty climax always seemed likely.
 
Jose Mourinho, who saw his side beaten by Liverpool at the same stage two years ago, had been accurate in his pre-match prediction that, with Ricardo Carvalho missing from Chelsea's defence, Peter Crouch would start in a Liverpool side aiming to repeat the aerial assault that yielded a 2-0 victory in the Premiership earlier this year.
 
Dirk Kuyt had a goal disallowed for offside
but scored the winning penalty [EPA]
More surprising was Rafael Benitez's decision to dispense with the services of Xabi Alonso in a midfield reshuffle that saw Steven Gerrard restored to a central role and Jermaine Pennant asked to patrol the right flank.
 
With Salomon Kalou operating in a five-man Chelsea midfield, Mourinho appeared to have decided that cutting off the supply to Crouch at source represented his side's best chance of preserving their first-leg advantage.
 
The stifling tactics worked efficiently enough at the outset, but an uncharacteristic lapse in Chelsea's defensive discipline gave the home side the opportunity to level the aggregate scores after Gerrard was chopped down on the left of the box.
 
Cole was fortunate to be spared a booking but his team were not to escape punishment for his ill-timed challenge.
 
Set piece
 
Preoccupied by the threat posed by Crouch and Dirk Kuyt hanging around the far post, nobody in a blue shirt appeared to have noticed Agger making his way to the edge of the area.
 
Gerrard did and his square pass was met with the sweetest of left-foot shots from the Danish defender, the low, first-time strike denying Cech the time to get back across his goal before the ball had nestled in the back of the net.
 
The delirious jubilation that followed spoke volumes about the intensity of the rivalry that now exists between these two clubs.
 
The celebrations might have been cut short 10 minutes later when a stray pass from Javier Mascherano allowed Kalou to play Didier Drogba into the box.
 
But from 15 yards, Africa's player of the year opted for power when placement might have served him better and Reina was able to make a block that was important but straightforward.
 
The normally deadly Didier Drogba
could not convert at Anfield [EPA]
Liverpool had another let-off five minutes before the interval, when Michael Essien was unable to find the target from beyond the back post after Drogba had headed on Frank Lampard's corner.
 
With the added stimulus of attacking the Kop end, the home side began to generate openings from open play at the start of the second half.
 
Pennant's cross allowed Crouch to produce his first effort on target, a back-post header that Cech needed two attempts to gather, shortly before Kuyt sent John Arne Riise's delivery clattering against the bar.
 
Increasingly effective before being forced off injured, Pennant was also unfortunate to see his 71st-minute shot deflected over the bar by Essien's outstretched leg.
 
The best of the second-half chances fell to Chelsea, however, Drogba contriving to lift Ashley Cole's cut-back over the bar from close range with a quarter of an hour left.
 
Liverpool were denied again in the first period of extra-time when Cech's speed off his line allowed him to thwart Kuyt, sent clear by the inexhaustible Mascherano.
 
The Czech goalkeeper then had to dive to his right to keep out substitute Alonso's fierce drive and although Kuyt turned in the rebound, he had strayed into an offside position.
 
Two minutes from penalties, the Dutch forward saw another chance blocked by Geremi. But ultimately his tireless efforts were to get their reward.