Poulter was ‘gifted’ his final round robin encounter when American opponent Kevin Chappell withdrew on the ninth green of their match complaining of back pain.
Poulter, and winner of the event in 2010, had been 3-up at the time but it was clear Chappell was struggling.
“I needed to get something out of the match and being 3-up playing nine and it turned into a strange finish,” said Poulter.
“I was just over the back of the green in two, trickled down my third shot stiff. Kevin then missed his putt and I was walking off the green and turned around and he said, ‘Listen, I can’t go anymore holes as my back is not right’.
“He’s obviously got some kind of an issue going on. I had warmed up in the fitness trailer this morning alongside him and there did not seem to be a problem.
“He called his physio down by the ninth green and then got some treatment on the 10th tee.
“So, you never like to win in that fashion. You want to take it as far as you need to take it to obviously win your match.
“But then I had control in that match. I felt pretty good. Hopefully he comes back pretty soon.”
Should the current World No. 64 ranked Poulter win his match over Oosthuizen he then needs to also defeat the winner of the Kuchar and Kevin Kisner encounter and make into the last eight for a Masters invitation.
Sweden’s Alex Noren takes on Patrick Reed in a Europe-v-USA fourth round match with Noren winning his group 1-up over American Tony Finau while Reed bundled out fellow Texan Jordan Spieth 2 & 1.
Noren, 35 lost last year in the quarter-finals to eventual champion, Dustin Johnson and is sure to have the crowd against him Saturday morning in the Texas capital.
“The Ryder Cup is a long time from now and while many may see my match with Patrick as a potential Ryder Cup showdown, all I need to think about holing putts like I holed today and I should be fine,” said Noren.
“I have putted decent all three days and I like I haven’t been out of from the tee but to hole the putts near the end of my match both yesterday and today is some of my best putting for some time.
“I’m just so pleased to work my way into the top-16 and now have a chance as I went so close last year losing out to Dustin in the quarter-final.
“Also, there is a lot of World Ranking and Ryder Cup points for so that now makes the weekend even more exciting.”
And England’s Ross Fisher had no answer to American Matt Kuchar who was 2-up when he aced the par-3 seventh hole on route to a comfortable 6 & 4 success.
Saturday AM (US time) Round Four match-ups:-
Matt Kuchar vs Kevin Kisner
Ian Poulter vs Louis Oosthuizen
Patrick Reed vs Alex Noren
Cameron Smith vs Tyrrell Hatton
Justin Thomas vs Si Woo Kim
Sergio Garcia vs Kyle Stanley
Kiradech Aphibarnrat vs Charles Howell III
Brian Harman vs Bubba Watson