HALFTIME: Notre Dame 41, Duke 26 GREENSBORO, N.C.—After 20 minutes of play, No. 2 Duke trails No. 11 Notre Dame 41-26 in the ACC semifinals. The Blue Devils have been paced by Jahlil Okafor's 15 points and four rebounds, as the rookie center has largely been the reason Duke is not down by more heading into the break.A day after playing one of its most dominant games of the season, the Blue Devils have come out flat in the early going, allowing the Fighting Irish to have their way inside and break any zone or man-to-man defense Duke has attempted. The sole bright spot for the Blue Devils—they have held Notre Dame's best player in check.Senior captain Quinn Cook switched to guard Notre Dame star guard Jerian Grant after Justise Winslow allowed an early drive to the basket. In Duke's Jan. 28 loss to the Fighting Irish, Grant went for 23 points, but in its blowout 90-60 win Feb. 7, Grant went for just seven points. Although the Blue Devils have not executed well on offense, Cook has done a solid job of guarding Grant, allowing the senior guard just five points.But although Grant has been a non-factor offensively, Demetrius Jackson has been all over the place for Notre Dame. After scoring just 11 in the teams' last clash, Jackson has been aggressive, taking Duke point guard Tyus Jones to the hole for 11 points.After scoring 44 points in the paint against N.C. State Wednesday, the Blue Devils tried to go back to the lane early against Notre Dame. But the Fighting Irish were prepared and have turned the tables on Duke.Through the first 20 minutes, Notre Dame outscored the Blue Devils 30-14 in the paint, using drives from Jackson and short jumpers from Bonzie Colson—who leads his team with 14 points—to attack Duke's interior. On the other end of the floor, Zach Auguste forced Okafor to take several fade away jumpshots before the Blue Devil big man began backing Auguste down into the paint to get Duke back in the ball game.Observations from the first half: The Fighting Irish took the ball to hole early and often—their first four baskets were layups The Blue Devils had five turnovers in the entire game against N.C. State—they had five in the first eight minutes Friday. Pat Connaughton, who knocked down four-straight 3-pointers in the Fighting Irish's quarterfinal win against Miami, was held to zero points in the first half. As much as Duke has shot itself in the foot on defense, Notre Dame has been solid in preventing the Blue Devils from converting many easy shots. Although Duke is shooting 41 percent from the floor with 14 points in the paint, nobody besides Okafor has gotten going down low. The freshman, Cook and Tyus Jones are the only Duke players to score so far. The Blue Devils average 7.7 made 3-pointers per game. They have one so far Friday.