Ronnie O'Sullivan won six out of seven frames to book his place in the last eight of the World Championship at the expense of gutsy Welshman Ryan Day.
O'Sullivan was made to battle hard against Day
The 'Rocket' won 13-10 having gone into the final session 9-7 down.
Fortune was not favouring Day, missing an easy red in the 17th frame and then seeing his cue ball leap over the pink in the 18th.
O'Sullivan won four out of the next five, hitting breaks of 68, 51 and 75, to set up a tie against Mark Williams.
The Essex star said he was fortunate to beat his 26-year-old opponent.
"It was a tough game and I'm lucky to be through. He had his chances, but wasn't able to finish me off," said O'Sullivan, champion in 2001 and 2004.
The 30-year-old added that he was looking forward to facing another Welshman in Williams: "I need to raise my game a little because he's playing well."
Day rued a series of miscues during the match.
"The dome of the tip had got a bit hard and wasn't taking the chalk," said the 26-year-old from Bridgend.
"It's been happening on the practice table as well.
"I'm gutted to have lost. I felt I played really well and kept telling myself I was still in the match when Ronnie came back."
R Day (Wal) 10-13 R O'Sullivan (Eng)
41-77 5-88 75-4 (58) 66-33 88-5 0-140 (140) 69-0 (68) 28-105 (65) 22-92 13-98 (82) 58-1 104-19 (104) 80-0 (80) 36-114 71-60 69-36 59-75 (Day 58) 60-76 (Day 56) 30-69 (68) 5-100 (51) 31-103 63-50 1-75 (75)