Halftime: Duke 42, UNLV 26 LAS VEGAS—Grayson Allen has struggled offensively this season, shooting just 35.7 percent as he battles through turf toe.Unfortunately for UNLV, the junior looked healthy for Saturday's game.Allen started 5-of-7 with 12 points as the No. 5 Blue Devils opened the game on a 20-3 run to immediately take control against the Runnin' Rebels at T-Mobile Arena. Duke finished the period with a 42-26 advantage, overwhelming UNLV with its aggressiveness on both ends of the court. Allen's soaring one-handed jam on a feed from Matt Jones sent the capacity crowd of 18,000 in the arena's first college basketball game ever into a frenzy, giving the Blue Devils a 16-3 advantage just 5:27 into the contest. The All-American finished the period with 17 points on 6-of-10 shooting coming off a 2-of-10 performance Tuesday against Florida.Duke's defense fueled its hot start. The Runnin' Rebels struggled to finish inside against the Blue Devils' length and committed 13 turnovers. Many of those giveaways allowed Duke to get out in transition and turned into points for Allen and sophomore Luke Kennard on the other end. Kennard is having another strong game so far, with nine points and four rebounds.Although UNLV went on a 6-0 run after falling behind 20-3 and a 11-2 spurt after going down 36-15, the Blue Devils responded with crisp ball movement. Duke shot 48.5 percent in the opening 20 minutes and looks to be well on its way to its eighth win in a row. Here are some observations from the first half: Although freshman Jayson Tatum scored 22 points off the bench against Florida, he did not start Saturday's game. Chase Jeter started alongside Amile Jefferson up front as he played in his hometown and posted no points and one rebound in six minutes.Tatum got off to a slow start offensively for the third straight game, missing his first three shots. He got on the board with a pair of free throws late in the period and finished the half with two rebounds and an assist in 11 minutes.Freshman Marques Bolden played five minutes down low in the first half, posting four points after a two-minute outing against Florida. Duke experimented with its lineups frequently, using four-guard sets multiple times and also utilizing Bolden alongside Jefferson in the paint. The Blue Devils established a 20-point lead with 5:42 left in the first half in one of their cleanest performances this season.