In hindsight, though, perhaps we should have seen something like this coming. Hidden behind the ridiculous efficiency of Zion Williamson, the Blue Devils have shown signs they were vulnerable in recent weeks.SN’s MARCH MADNESS HQLive NCAA bracket | Live scoreboard | Full TV scheduleWhen Zion was out injured for six games, his teammates shot 42.9 percent overall and 28.1 percent from beyond the arc. For the season, Duke is 47.8 percent overall and 30.5 percent on 3-pointersIn the ACC Tournament, non-Zion players completed 54 of 141 shots (38 percent). Williamson, meanwhile, shot an incredible 33 of 43 (77 percent), making his teammates’ woes insignificant. But when Williamson’s shot fell slightly less often than normal against UCF — in part because of the presence of 7-6 center Tacko Fall — Duke struggled to make up for his dip in production. Williamson shot 50 percent from the floor against UCF, well below his recent level of efficiency, but still better than the average college basketall player.Tre Jones went 5 of 15. Barrett shot 6 of 15. Only Reddish, who had been scuffling of late, delivered consistent offense outside of Williamson, finishing 5-of-8 shooting. Non-Zion players combined to shoot 18 of 43 (42 percent) against UCF.In the end, having several NBA-caliber players in crunch time made the difference for Duke.DECOURCY: Tacko vs. Zion is a heavyweight bout we haven’t seen beforeWith the Blue Devils down four with about a minute remaining, Reddish drained a transition 3-pointer to pull within one of the Knights. Two possessions later, Williamson fouled out Fall with an and-one layup; Barrett followed up the would-be tying free throw with a dunk to put the Blue Devils up 77-76. A final defensive stand ensured they would advance. Duke’s season almost ended against 9-seed UCF in a game many expected to be a blowout in favor of the Blue Devils.A clutch 3-pointer by Cam Reddish, a layup through contact by Zion Williamson and a second-chance bucket by RJ Barrett in the final minute were enough to stave off the Knights’ upset bid. UCF missed a pair of short-range looks before the buzzer to seal Duke’s 77-76 win on Sunday. But moving forward, Duke could be in trouble if Williamson doesn’t get more help. The competition, on paper, will only increase in difficulty from here. Williamson is being asked to shoot near 70 percent for his team to win comfortably — a risky proposition no matter how talented the forward may be.Barrett in particular has demonstrated he is capable of knocking down shots at a respectable clip, completing 45 percent of his attempts overall this season.For Duke to contend for a national championship, he must regain his best stroke soon — or get some of its other players to get him some offensive help.