Sahin double cancels out Tamas' early opener in third-round tie
The Baggies took an early lead when Gabriel Tamas punished a Brad Jones error in the third minute.
But cup holders Liverpool were level on 17 courtesy of another goalkeeping mistake, with Ben Foster uncharacteristically failing to keep out Sahin’s long-range shot at his near post.
The Reds’ young team looked a transformed side after their leveller and finally got the goal their vibrant performance had merited eight minutes from time.
It had a suspicion of offside but on-loan Real Madrid man Sahin's tap-in proved decisive.
Markus Rosenberg was handed his full Hawthorns debut as Steve Clarke made five changes from the Reading win.
The Baggies got off to a flying start – breaking the deadlock inside three minutes.
Reds keeper Jones inexplicably dropped Liam Ridgewell’s angled free-kick into the heart of the Liverpool penalty area and Tamas pounced on the rebound to volley his first goal in nearly two-and-a-half years into the empty net.
Confidence was oozing through the home team and, just three minutes later, Romelu Lukaku cut inside the box from Dorrans’ pass and saw his 15-yard drive deflected just wide by Jamie Carragher.
Moments later, Lukaku chased what seemed a lost cause before outmuscling Carragher and teeing up Rosenberg. The Swedish international let fly from a tight angle and saw his effort brilliantly blocked at the near post by Jones.
Completely out of the blue, Liverpool could have been level on 11 when Samed Yesil flashed a free header wide from Oussama Assaidi’s left-wing centre.
But they did equalise six minutes later – thanks to another goalkeeping error.
Foster had not been beaten in six previous home games but would have been disappointed with letting Sahin’s speculative 30-yarder beat him at his near post. The Albion No.1 appeared to have the shot covered but could only push the ball inside his near post.
The goal injected new life into Liverpool’s veins and their young side took control.
Tamas made another telling contribution, this time in his own box, on 21 when he cleared Daniel Pacheco’s goalbound shot.
Albion then suffered an injury blow, with Ridgewell being replaced by Craig Dawson.
Another swift Liverpool move culminated in Assaidi cutting inside Billy Jones and shooting tamely at Foster from an acute angle.
Youssouf Mulumbu put Albion back on the front foot when, after some nifty footwork, he played the ball into the right-hand channel. However, Jones was alert to the danger and rushed out of his area to beat Lukaku to the ball and clear.
Lukaku looked a constant threat in and around the Liverpool box and squeezed in a shot on 38 which Jones dived to hold low to his left.
Albion finished the half strongly. Dorrans saw a ferocious, acute free-kick clip Andrew Wisdom in the Liverpool wall and flash wide of the far post. Then, after good work by Fortune, Mulumbu saw a goalbound shot blocked by Carragher.
The second half started in end-to-end fashion – but it was Liverpool who looked the most dangerous.
Foster knew little about Yesil’s swirling 20-yard rocket which bounced down off the keeper’s frame and, thankfully, over the bar
On 52, Pacheco went even closer with an audacious 25-yard curler which beat Foster before clipping the top of the bar.
Albion’s first shot of the half came from Rosenberg, who was well wide with a first-time effort from distance.
Rosenberg was much closer with his next shot, drawing a fine save out of Jones with a 25-yard curler from Fortune’s lay-off.
Back came Liverpool. Pacheco nut-megged Thorne before seeing his awkward 30-yard drive pushed wide by Foster.
Clarke made his second change of the evening on 70, this time tactical, replacing Lukaku with Long.
Whatever had gone before, Foster was back to his best on 74 when he produced a stunning reflex save to keep out Sebastian Coates’ stab from Assaidi’s dangerous free-kick delivery.
Albion were enjoying plenty of possession in and around the Liverpool box but struggled with their final ball or decision-making.
And it was the Reds who struck the next blow. With just eight minutes left, sub Suso was allowed to surge forward before slipping in Assaidi and his low cross was tapped home by the unmarked Sahin, who looked suspiciously offside.
Albion almost equalised immediately when Fortune saw his vicious volley from the tightest of angles brilliantly saved at his near post by Jones.
ALBION (4-2-3-1): Foster; Jones, Tamas, Olsson, Ridgewell (Dawson 22); Thorne, Mulumbu; Fortune (El Ghanassy 88), Dorrans, Rosenberg; Lukaku (Long 70). Subs not used: L Daniels (gk), Berahino, McAuley, Yacob.