CORAL GABLES, Fla. – Duke coach Mike Krzyzewski looked down his bench midway through the first half, trying to check on Nolan Smith.
Small problem: Smith wasn't there.
"That's not a good thing," Krzyzewski said.
Fortunately for No. 5 Duke, Smith returned in plenty of time.
Playing with a scratched left eye, the senior guard scored 16 of his 18 points in the second half, Seth Curry added 16 points and five steals and Duke extended its Atlantic Coast Conference lead by holding off Miami 81-71 on Sunday night.
"It was closed for a while," Smith said. "I really didn't know what was going on at the time. They just numbed it up a bit at halftime. Now I feel fine."
His teammates more than helped the cause.
Kyle Singler scored 14 and Mason Plumlee 12 for the Blue Devils (23-2, 10-1). Duke's record after 25 games matches its best since the 2005-06 season.
It turned out to be a nifty gift for Krzyzewski, on his 64th birthday.
"It's unbelievable being 52," Krzyzewski said. "I know I look a lot older."
Reggie Johnson scored 16 points on 7-of-9 shooting for Miami (15-10, 4-7), which was bidding for its first four-game ACC winning streak since February 2008. The Hurricanes fell to 1-17 since 2000 against teams ranked No. 5 or higher, the lone win coming against Duke three seasons ago.
The Blue Devils didn't let that happen again, building a double-digit lead midway through the second half and controlling the game from there.
"I thought our guys competed," Miami coach Frank Haith said. "Obviously, we had some breakdowns defensively and gave them some open looks. ... A lot of broken plays."
Miami got within six points twice in the final minute, only to have Tyler Thornton hit two free throws on ensuing Duke possessions to keep the Hurricanes out of reach. Duke finished 17 of 21 at the foul line, compared with 5 of 6 by Miami.
"We've got to figure out a way to get to that free throw line," Haith said.
Malcolm Grant also scored 16 and Durand Scott added 10 points and a game-high eight assists for the Hurricanes, who play four of their last six regular-season games on the road.
In short, when Smith got rolling, everything started to click for Duke.
He went to the bench with two fouls — and a bigger problem — with 13:08 left in the opening half.
After fouling Johnson, Smith was inadvertently poked in the eye, and that was Duke's bigger concern. It turned out to be a missed opportunity for Miami.
The Hurricanes were down 16-15 when Smith left the game, and the deficit was 31-27 when he returned, in part because Miami's best scorer was on the bench as well. Grant scored 12 points and hit three 3-pointers in the first 6:53 of the game, then sat out the final 9:32 until halftime after getting his second foul.
"Frustrating," Grant said. "I'm not out there able to help my team in every way possible."
Smith didn't make his first field goal until 15:16 remained in the game, a pull-up in transition. Once he started, the scores came in bunches. He made three more shots in the next 3 minutes, capped by a driving layup after Julian Gamble missed a dunk at the other end to give Duke what was then its biggest lead, 61-51 with 11:34 remaining.
Curry carried Duke in the first half with 13 points. Smith assumed the workload from there.
"We came up with big stops," Curry said. "At times, they were getting whatever they wanted, with open shots and Johnson inside. When we needed them the most, we came up with the stops."
Duke hadn't played since Wednesday's 79-73 home win over North Carolina, a game in which the Blue Devils fought their way back from an early 16-point deficit.
They started slowly Sunday as well. Miami made its first four shots, capped by Grant connecting on a 3-pointer while getting fouled by Smith for a quick 10-4 lead.
Things calmed down quickly.
Duke scored the next seven points, and although Miami reclaimed the lead six more times during a back-and-forth first half, the Hurricanes' biggest edge came at 37-33 after Rion Brown made a 3-pointer with 2:46 left.
Duke closed the half on a 9-0 run, and after Miami got within one early in the second half, another 9-0 burst — fueled when Smith finally found his scoring groove — pushed the Blue Devils' lead back to double digits.
"Difference in the game," Haith said.
(This version corrects to 1-17 against top-5 teams)