Barry Hawkins followed up his victory over world number one Mark Selby by edging ahead against Matthew Stevens in their second-round Crucible clash.
In an absorbing morning session at the Betfred.com World Championship, 32-year-old Dartford man Hawkins gained an early 3-0 lead, maintaining the form which saw him made no mistake against an injured Selby in the first round.
Qualifier Hawkins was pegged back to 3-3 and then ground out a long frame before regaining fluency to pull two frames clear at 5-3.
Welshman Stevens, runner-up in 2000 and 2005, fired in a 59 before missing a red in the opening frame, and Hawkins matched the break but missed the black off its spot.
Stevens attempted to double in the black, left it hanging by the yellow pocket, and Hawkins made no mistake with his second chance.
He surged three frames clear with runs of 69 and 64, before Stevens got even, helped by breaks of 85 and 101.
Hawkins held his nerve in a gruelling 47-minute frame to restore his lead, before a 65 gave him the cushion to take into tonight's second session.
With 13 frames required for victory and a quarter-final place, only a Hawkins whitewash of the evening's eight frames would ensure a result on Sunday, with the match scheduled to reach its conclusion on Monday afternoon.
It was a big day for the Welsh in Sheffield, with Neath's Jamie Jones level at 4-4 against Widnes' Andrew Higginson after their morning session.
The afternoon will see another Welshman, two-time champion Mark Williams, return to face Ronnie O'Sullivan in their second session. Three-time former winner O'Sullivan carried a 5-3 lead into the session, as did Ali Carter as he resumes against last year's losing finalist Judd Trump.