Matthew Stevens set up a quarter-final meeting with Shaun Murphy after a hard-fought 13-9 win over qualifier Mark Allen at The Crucible.
Stevens has an excellent record at The Crucible
Stevens resumed with a 9-7 lead, and won the opening two frames of the session with breaks of 83 and 64 to put the pressure on the 21-year-old.
Allen responded well initially, digging deep to close to just 11-9 behind.
But a missed black in the pivotal 21st frame cost him as Stevens pinched it before making a gritty 40 in the last.
Stevens needs a good showing at The Crucible to guarantee his top 16 place next season, and the Welshman looks somewhere near his best after a mediocre season.
Allen, who knocked out former champion Ken Doherty in the first round, showed his talent with some superb potting, but his inexperience was exposed by some questionable tactical decisions as the pressure grew.
I know I'm going in the right direction
"I missed quite a few blacks but I can't be too disappointed," said the world number 61.
"My two matches have shown I'm capable of competing with the top players now.
"I probably scored as well as Matthew, I just have to cut out a few mistakes. I know I'm going in the right direction and it's encouraging for the future."
The Northern Ireland player displayed real character in the second session, reeling off the final three frames to haul himself back into the match, but Stevens had too much know-how in the end.
"Mark kept me under a lot of pressure, but that black was a big shot to miss," said Stevens.
"But it's his first time here and I think he's an unbelievable player.
"I'll be the underdog against Shaun but I'm looking forward to it - I'm feeling good about myself."
Matthew Stevens 13-9 Mark Allen
78-1 83-34 (83) 65-16 84-21 (56) 18-101 (101) 0-105 (63) 0-118 (118) 112-22 (85) 101-0 (101) 76-9 71-6 0-85 (83) 79-57 (73, 57) 1-90 (78) 11-76 27-64 92-17 87-19 (64) 9-98 30-97 62-39 65-1