RALEIGH, N.C. (AP) -- Clemson struggled to get its offense running in high gear and spent much of Thursday night fighting to protect a slim lead. The third-ranked Tigers still did enough to stay unbeaten in the kind of game that often has slipped away in recent years.
Tajh Boyd threw for 244 yards and three touchdowns to help Clemson beat North Carolina State 26-14, winning its Atlantic Coast Conference opener on the road.
Clemson came in averaging 45 points and 490 yards, but didn't score its first touchdown until late in the first half.
''We had two or three scoring opportunities that we didn't convert on and just missed them. Just that simple,'' Clemson coach Dabo Swinney said. ''I thought we had a good game plan. I was pleased with how we were able to run the ball but disappointed with some execution in the first half. ... But we cleaned it up, we battled hard and got it to the second half and we ended up coming alive.''
Boyd's 30-yard scoring pass to Martavis Bryant capped a critical third-quarter sequence - including an apparent Wolfpack touchdown negated by an official's whistle - that allowed the Tigers (3-0, 1-0 ACC) to seize momentum in front of a hostile crowd.
Boyd found Bryant for another touchdown, with Bryant snatching the ball from defender Niles Clark for a 15-yard score that made it a three-possession game early in the fourth.
Sammy Watkins added 10 catches for 96 yards, helping Clemson finish with 415 total yards.
Shadrach Thornton scored the Wolfpack's first touchdown on a 21-yard run in the second for a 7-6 lead, but N.C. State (2-1, 0-1) couldn't complete the upset in coach Dave Doeren's first league game.
The Tigers entered Raleigh with their highest ranking in 25 years and a prime spot in the national championship chase. They also came in with memories of their inexplicably bad performance here two seasons earlier, when the Wolfpack scored 27 second-quarter points en route to a 37-13 rout of the then-No. 7 Tigers.
N.C. State followed that win with an upset of No. 3 Florida State here last year, and Doeren - the former Northern Illinois coach - said that history gave his veterans confidence they could do it again. But N.C. State's hopes of beating a top-10 team at home for the third straight season essentially ended in one frustrating sequence.
Receiver Bryan Underwood, who stepped out along the sideline earlier in the game to cut short a long run, sprinted around the right side for what appeared to be an 83-yard touchdown to tie the game at 13 midway through the third. But officials ruled Underwood stepped on the sideline at the Clemson 47 and blew the play dead, making it an unreviewable play - TV replays appeared to show him remaining inbounds - that led to boos raining down from the Carter-Finley Stadium stands.
''It was right in front of me,'' Doeren said. ''He didn't go out of bounds. Unfortunately they blew it dead so they couldn't review it. It's an unfortunate deal. I know the guy felt bad about it. You can't do anything about it. That's just the way it is.''
Three plays later, Clemson's Vic Beasley knocked the ball loose from Pete Thomas on a sack for a fumble recovered by Spencer Shuey. Boyd and the Tigers' offense pounced on the opportunity, with Boyd hitting Bryant for the 30-yard score that made it 20-7 with 5:25 left in the quarter.
''I think for the offense we always go and find a way to make a play when it's needed,'' Boyd said. ''When we really need it, we go get it done. ... It was huge. We had to make sure we got something out of it.''
Bryant's impressive grab for his second touchdown on Clemson's next drive made it 26-7 with 11:27 left - and the booing over the Underwood call continued.
''It hurts, but hey, things happen in games,'' Underwood said. ''So you've got to bounce back with them, good or bad.''
Sam Cooper added an 11-yard touchdown catch with 2:23 left in the second that gave the Tigers a 13-7 halftime lead they wouldn't relinquish.
Thomas threw for 213 yards on 20-for-36 passing for the Wolfpack and also ran for a late 4-yard score. N.C. State finished with 378 total yards, but failed to convert its first eight third-down tries and finished 3-for-16 for the game.
Follow Aaron Beard on Twitter at http://www.twitter.com/aaronbeardap