WASHINGTON—Maybe that tight rotation and lack of depth finally caught up with Duke. Sure seemed like it while the reigning national champion let a 16-point, second-half lead evaporate in an overtime loss to Notre Dame at the ACC Tournament.Looking spent down the stretch, 19th-ranked Duke lost to the Fighting Irish 84-79 in the ACC Tournament quarterfinals Thursday.V.J. Beachem scored 19 points, including a couple of key 3s late in the second half, for fourth-seeded Notre Dame (21-10), which also beat Duke a year ago en route to winning the league tourney and earlier this season at Cameron Indoor Stadium. In all, the Fighting Irish have now won five of the teams’ last six meetings.Zach Auguste contributed 19 points and 22 rebounds for Notre Dame.Grayson Allen led defending national champion Duke (23-10) with 27 points, but there wasn’t much help, in part because of foul trouble for an already thin rotation.Duke shot only 30 percent in the second half and did not get a lot all afternoon from 7-footer Marshall Plumlee, who was wearing a mask a day after breaking his nose. He finished with only two points and four rebounds before fouling out. Chase Jeter picked up his fifth in overtime, while star freshman Brandon Ingram was stuck with four fouls in the late going.In Friday’s semifinals, Notre Dame will take on No. 7 North Carolina, the team it beat in last season’s conference tournament final. UNC advanced by beating Pittsburgh 88-71 earlier Thursday.Duke has gotten by with what essentially has become a six-man rotation, the sort of thing that means there is not much to choose from in the way of experienced depth when top guys get hurt or in foul trouble. And it also becomes more difficult to deal with at this time of year, when games come fast and furious.The exhaustion might finally have caught up to the Blue Devils midway through the second half. Up 64-48 midway through the second half, they let that dwindle to 64-62 on Auguste’s inside basket with 4 1/2 minutes left in regulation. During the 14-0 run for Notre Dame, Duke went scoreless for 7 1/2 minutes, going 0 for 8 on field-goal tries, 0 for 4 at the line.And when Beachem made a 3 with 2 1/2 minutes to go, he put Notre Dame ahead 67-66 – its first lead since 35-34 with 5 minutes left in the first half.Beachem then sank another 3 with 64 seconds left, making the score 70-all, and it stayed that way until the extra period, when he came up with yet another shot from beyond the arc.By then, Notre Dame was not going to let up – and Duke did not have enough left to make another push.After putting up 50, 42 and 45 points in its first three halves of the tournament, Duke managed only 34 in the second half plus OT on Thursday. NOTES—Lost four of its last seven games. … Plumlee is the only player to have started all 33 games for the Blue Devils this season. … Entered the day making 9.2 3-pointers per game, the highest mark in the league. When Jones made a 3 in the first half, it was his 70th of the season, making him, Allen and Ingram the first trio in school history with at least that many in the same season….Notre Dame Won at home against UNC 80-76 in February. … Came in averaging only 9.1 turnovers, third-fewest in the country; the Irish had 18 against Duke.