Ronnie O'Sullivan beat Mark Williams 6-5 on Wednesday and will meet Mark Selby in the quarter-finals of the Snooker Masters at the Alexandra Palace, London.
O'Sullivan will face three-time champion Selby, who thrashed Ricky Walden 6-0, reports Xinhua.
The 40-year-old took a break from competitive snooker for several months at the start of this season, returning to action at last month's German Masters qualifiers. He sharpened his game by competing at last week's Championship League, winning eight consecutive matches.
He produced spells of brilliant snooker at times on Wednesday, though Williams made life tough for him, particularly in the middle of the match when the Welshman won four frames in a row.
O'Sullivan, who has won the Masters five times and reached a record 10 finals, is suffering from a slipped disc in his lower back which he believes has created an imbalance in his cue action.
"We both struggled at times and missed a lot. I didn't feel nervous and it was nice to make a break in the last frame," he said.
"I played a few exhibitions over the summer and I was playing well, but then I hurt my back and now I can't get on the shot right. Maybe I'm just going through a period of playing poorly but that seems to have coincided with the back problem."