"It's no surprise to me that Stephen is there as he is a great player. He is a great champion and it is a privilege to play him. At this level it is all about competing against the greatest players, it should be a superb match."
O'Sullivan's victory brings to an end the run of Liang, whose entertaining style made him a real favourite with the Sheffield crowd.
Liang defeated Ken Doherty and Joe Swail on the way to the last eight and O'Sullivan was impressed with how the 21-year-old coped with his debut campaign at the Crucible.
"It was a different challenge to play him because he is new to the scene," said O'Sullivan. "You don't know what type of game he is playing.
"He goes for a lot of shots but he gets them, he is a fantastic potter. He is here to stay."
O'Sullivan says he is focused on victory
The pair were locked at 4-4 after Tuesday's opening session but O'Sullivan produced some virtuoso snooker on Wednesday morning to take control of the contest.
In the first four frames he made five breaks of 50 or above and he then added a 138 clearance and a fluent 86.
Liang, who continued to display his attacking instincts but paid the price for his mistakes, won a scrappy penultimate frame but O'Sullivan won the last to take the six-frame advantage into the final session.
O'Sullivan lost the opening frame of the evening and was far from his fluent best before eventually securing the next on the pink.
The 32-year-old then lost position on a break of 54 to allow Liang in to steal the 19th frame with a run of 36 and the Chinese qualifier was first in with a break of 41 in the next.
But Liang crucially missed a black to the corner pocket and O'Sullivan took advantage with the 79 break to progress.
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