Duke will need to improve its free throw shooting. Beyond the arc: Three takeaways from Duke's comeback win against Portland State Duke stumbled out of the gates to open the Portland action in the PK80 Invitational, needing a second-half comeback to down Portland State 99-81. Three Key Takeaways: 1. Allen and Trent continue to struggle shooting After hitting 7-of-11 attempts from beyond the arc and scoring a career-high 37 points against No. 2 Michigan State Nov. 14, Grayson Allen has gone ice cold, hitting just two of his last 16 shots from downtown. Gary Trent Jr. also has been unable to get his shot to fall, getting just 23.8 percent of his 3-point attempts to fall while shooting just 29.2 percent from the field. 2. Marques Bolden could be a factor Following a dud of a freshman campaign, Marques Bolden had a slow start to the season, but could end up being a factor if he keeps up the level of play he flashed Thursday. Bolden had a breakout performance of sorts, tying his career-high in points with eight while adding a career-high 10 rebounds and three blocks on the night. If he continues to play strong defense and crash the glass, Bolden could earn more playing time as a veteran filling in for freshmen Marvin Bagley III and Wendell Carter Jr. down low. 3. Alex O’Connell sparks the offense Down by six with less than seven minutes left in the first half, the Blue Devils turned to O’Connell to ignite the offense. The freshman sharpshooter nailed two of his first three shots, including four of his six overall to help jump-start the Duke offense and allow them to pull ahead of an upset-minded Portland State team. Look for head coach Mike Krzyzewski to continue to use O'Connell as a shot in the arm to help Duke break out of slumps mid-game. Three key stats: 1. 73.8 percent from the line Somehow, Thursday’s 31-for-42 performance from the charity stripe was the Blue Devils most efficient performance this season. Duke entered the contest shooting just 61.7 percent from the free throw line, tied for 323rd out of the 351 teams in Division I. 2. 22.2 percent from beyond the arc The Blue Devils struggles from downtown continued Thursday with a third-consecutive sub-30 percent performance. Allen’s inability to convert has stagnated Duke’s perimeter offense and forced it to rely on the interior. If the Blue Devils struggles continue, Duke could find themselves in trouble if they end up playing 6-foot-11 center Mo Bamba of Texas Friday. 3. Plus-12 rebound margin Duke continued its dominance on the glass, grabbing a season-high 49 rebounds—including 15 boards on the offensive end. Bagley, Carter and Bolden all held their ground in the post, combining for 35 rebounds in Thursday's victory. Three key plays: 1. O’Connell layup, 5:26 remaining in the first half After Portland State stretched its lead to eight with less than seven minutes remaining, O’Connell made a spectacular spinning layup to cut the lead to six and spark the Blue Devils' offense. 2. Bagley Tip Shot, 17:01 remaining in the second half Down by six early in the second, Bagley would not let Portland State extend its lead. Bagley grabbed an offensive rebound, then tipped in his own missed layup to cut the lead to four. 3. Carter layup, 11:28 remaining in the second half Trying to extend a five-point lead, Allen went up for a layup in transition and dished the ball under the basket to a wide-open Carter, who finished the shot and got fouled. Carter followed the play by hitting the free throw, giving Duke a 70-62 lead. Looking forward The Blue Devils' streaky shooting from the field and the free throw line could cause trouble against tougher opponents later in the tournament, including Texas on Friday and either No. 7 Florida or No. 17 Gonzaga, if they get past the Longhorns. Duke needs to continue to dominate down low and get Allen and Trent back on track this weekend.