After suffering defeat to Thongchai Jaidee on the opening day, Poulter made an early exit at the hands of his second opponent, who claimed a one-up victory.
Having picked up four points out of four at last year’s Ryder Cup in the same format, the 37-year-old was expected to be among the challengers, and was upset at his performance.
“I have no excuses,” Poulter said afterwards. “There is no excuse for that display of golf over the last two days.
“It was simply disgusting, disgraceful and there’s no explanation. It is simply not good enough. I should have been able to finish the match off.
“My concentration was simply not there and therefore you make mental errors when you have not used your brain. It’s completely unacceptable.”
Aiken had earlier lost by the same score to Jaidee and was relieved to make it through to the knock out stages by bouncing back with a win.
“It’s fantastic to be here for the rest of the week,” stated the South African. “It all starts again tomorrow, another 36 holes.
“I had two tough matches today – Thongchai this morning – we played some really good golf, the back nine, every hole was won with a birdie pretty much.
“Then this afternoon against Ian, I got off to a good start and got it to two-up, but as you expect from him, he came back.
“All square with two to play, and fortunately I just didn’t make any mistakes on the last couple of holes and he made an error on the last.”
Defending champion Nicolas Colsaerts is also safely through, recovering from an opening day defeat to beat Kiradech Aphibarnrat 3&2.
“I played a little better of course,” noted the Belgian. “I kept the ball in play a bit more than yesterday. That was the plan, so mission accomplished.”
Branden Grace was top of Colsaerts’ group, winning both of his matches, while Aphibarnrat is on the plane home.
Graeme McDowell, the highest ranked player in the event and last year’s runner-up, finished top of the Ballesteros pool after seeing off Stephen Gallacher 4&2.
He will be joined in the next stage by Branden Grace, who also beat Gallacher to take his place in the round of 16.
Brett Rumford continues his chase for a third successive European Tour win, taking second in the Player group after beating Jamie Donaldson before a 3&2 defeat to Gonzalo Fernandez-Castano.
Shane Lowry birdied the second extra hole of a playoff to finish top in his pool ahead of Peter Hanson, while Richard Sterne and Bo Van Pelt have also qualified.
Francesco Molinari and Felipe Aguilar both came through the first round, while Scott Petterson and Carl Jamieson complete the last 16 line-up.
McDowell and Van Pelt meet on Saturday, while Colsaerts’ bid to defend his title continues with a clash against Fernandez-Castano.