The top-seeded Blue Devils returned to the round of eight for the first time since 2004, with Kyle Singler and Jon Scheyer helping them pull away in the second half last night for a 70-57 win over Purdue in the South Regional semifinals.

Singler scored 24 points and Scheyer added 18, snapping out of a shooting slump just in time.

Duke (32-5) will play third-seeded Baylor in tomorrow’s regional final after clearing a nagging hurdle that had some wondering if the mighty program was losing its edge.

The Blue Devils had lost in the round of 16 in three of the past five seasons, but now stand one victory from their 11th Final Four appearance under coach Mike Krzyzewski.

Duke keeps marching through the NCAA Tournament while other favorites are falling by the wayside.

Scheyer, Duke’s leading scorer, was 5 for 18 from the field in Duke’s first two NCAA Tournament games. He went 5 for 9 in the second half after missing his first six shots and also went 7 for 8 from the foul line.

Brian Zoubek grabbed 14 rebounds and Duke dominated the Boilermakers inside, as expected. The absence of injured do-everything forward Robbie Hummel finally caught up with fourth-seeded Purdue (29-6), which lost in the regional semifinals for the second straight season. Hummel tore his right ACL in late February and watched last night’s loss in street clothes from the bench.

JaJuan Johnson scored 23 points and E’Twaun Moore added 18 for the Boilermakers. No other Purdue player reached double figures and the team shot 37 percent (20 of 54).

The Blue Devils missed 22 of 29 shots, had 11 turnovers and led, 24-23, only because of a 29-13 edge in rebounding. Scheyer was 0 for 6 from the field, continuing his slump after going 1 for 11 in Duke’s second-round win over California.

Scheyer swished a 3 from the wing with 17:52 left, but Moore hit a straight-on 3 about two minutes later to tie it at 31.

Duke started to build a lead after that, and Singler’s 3-pointer with 11:55 left put the Blue Devils up, 40-35.