Ten changes sa wthe Potters put out a reserve side and they were made to pay as defensive errors gifted Pompey the game, and a place in the last 8 of the Carling Cup.
Turkish star Tuncay was in the side and trying to force his way into the side for Saturdays game against Wolves and he burst through after eight minutes. After collecting the through ball he back heeled into the path of Lawrence but the Irishman couldn't collect the pass and the chance was gone.
Uruguayan Diego Arismendi was impressive, on only his second start, and on eight minutes he cleared the danger after Higginbotham blocked Webber's shot.
Piquionne was a thorn in the City side all night and he was put clean through on nine minutes. Showing a lack of confidence he waited for support before rolling the ball across goal where Griffin was able to clear away.
The Pompey striker had an extra spring in his step on 16 minutes as he headed home after Belhadj found him at the far post.
Yebda went close to making it two moments after the restart and it needed a goal line clearance from Danny Pugh to stop the hosts running up a two goal lead.
On the half hour Arismendi played a one two with Lawrence before knocking the ball into the run of Griffin. The full back beat two defenders but his cross was overhit and flew into the stands.
City had one more chance prior to half time to go level when Lawrence collected Tuncay's pass and headed for goal. With Griffin on the overlap and Kitson and Tuncay pleading for a pass the winger smashed his shot well over the bar.
The second half started with Tuncay again finding Lawrence out on the wing. With many men waiting for the cross he produced a poor effort that was blocked by Belhadj and flew to safety. City were coming into the game either side of half time but disaster struck when Piquionne won the ball off Cort before pushing the ball into Webber who slammed the ball past Simonsen and into the net.
Three minutes later the game was all over as Simosnen dropped a cross at the feet of Piquionne, who made no mistake with a simple tap in to make it 3-0.
City knew they had to strike quickly to retain any hope of getting result and Arismendi went close when he got on the end of a Lawrence cross. His header was heading for the net before a diving defender blocked the effort and it was then cleared away.
Stoke did have the ball in the net on 73 minutes when Arismendi burst through the defence before squaring the ball to Tuncay at the back post. The Turkish striker tapped the ball into the net as the linesman raised his flag for offside.
Twenty-one-year-old powerhouse Arismendi was again involved on 78 minutes as Ashdown just beat him to Griffin's cross before the midfielder played a one-two with Griffin two minuites later. On collecting the return pass to produced a delightful cross that had Ashdown flying at to take away the danger. He challenged Sidibe and was awarded a free kick after hitting the deck.
Portsmouth scored a fourth on eighty two minutes as Whelan slipped in the midfield. Mokoena picked up the loose ball, rolling it through to sub Kanu. He rounded Simonsen and slotted home as the static Stoke defence stood and watched the misery be completed.
The final act saw seventeen-year-old Louis Moult was brought on for the final stages and showed good skill to dummy his way past Wilson. Just as the academy youngster thought he was in on goal he was hauled to the ground, Wilson receiving a booking for his cynical act.
Stoke: Simonsen; Griffin, Pugh, Higginbotham, Cort; Lawrence(Soares 75), Tonge, Arismendi, Whelan; Kitson(Sidibe 55), Tuncay(Moult 82)