North Carolina's Ryan Switzer made returning punts for touchdowns look easy last season. He's been frequently frustrated this time around.

"Most of the year, I've been bottled up," he said.

Switzer — who tied an NCAA single-season record with five TD punt returns as a rookie but has none this year — exemplifies how tough it's been for Atlantic Coast Conference teams to spring a big, game-changing return in 2014.

League teams have returned two punts and two kickoffs for touchdowns this season — not counting blocked punt returns — according to STATS. That's down from a combined total of 19 scores on kick returns in 2012 and 20 in 2013 while this year's average punt return of 7.3 yards is the lowest in at least a decade.

Coaches and players can't cite one specific cause for the downturn, either.

Some point to a strong year from punters who boot high kicks with long hang-times, rugby-style kicks that force returners to field a bouncing ball or directional kicks that drive returners into the teeth of oncoming tacklers.

Others note seeing different punt coverage formations that spread the field and allow tacklers a free run to the returner as soon as the ball is snapped.

"It's not like the old days where you're seeing the same punt unit like in the NFL (where) everybody has the same punt team basically," Miami coach Al Golden said. "We're seeing so many different formations, styles and blocking schemes, and guys running down on the snap because of the rules. Maybe it's finally caught up."

Making it all more surprising, the league brought back four returners — UNC's Switzer, Duke's Jamison Crowder and DeVon Edwards, and Miami's Stacy Coley — who earned all-ACC honors from the media or coaches last year.

Neither Switzer nor Coley, who returned a punt and kickoff for long touchdowns last year, have TD returns.

Crowder had a 52-yard punt return for a score against Syracuse and Edwards had a 99-yard kickoff return for a touchdown at Pittsburgh, though their return averages have dipped from a year ago.

"For those people that have run a lot back in the past, they probably don't get as many opportunities as they did when nobody really knew about you," Edwards said. "It is a little bit harder, just because people know who you are."

Virginia Tech coach Frank Beamer, North Carolina's Larry Fedora, Duke's David Cutcliffe pointed to strong punting as a major factor. Eight ACC punters rank among the top 35 nationally in average yardage per kick.

Then there are kickoffs, with teams being more content to take a knee in the end zone to start their drive at the 25-yard line. The percentage of touchbacks on kickoffs is at its highest rate since at least 2008 at 43 percent, up from about 37 percent in each of the past two seasons, according to STATS.

"The quality of the kickers with touchbacks and the height of the kicks on kickoffs has really made a difference this year," Georgia Tech special teams coach Ray Rychleski said.

Eddie Faulkner, North Carolina State's special teams co-coordinator, said those challenges have forced coaches to adapt.

The Wolfpack's focus on kickoff returns has been to consistently earn the best field position possible, even if that means repeatedly taking touchbacks. On punts, the emphasis is as much about securing the ball and avoiding negative plays as getting a big return.

"The coaching point is getting the kids to understand how to be smart in the game and say, hey, when our opportunity comes, we're going to maximize it," Faulkner said, "but we're not going to force the issue."

Switzer said he did that early this season with the Tar Heels. He had to change his approach after frequently finding himself waiting to field high-hanging kicks and surrounded by waiting defenders. He's focused now on staying patient and making whatever play is there, even if it's simply calling for the fair catch.

Switzer said he talks with Duke's Crowder, and the two are feeling the same headache.

"He's been a little frustrated," Switzer said. "But I told him at least he's got one."

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AP Sports Writers Will Graves in Pittsburgh; John Kekis in Syracuse, New York; Hank Kurz in Richmond, Virginia; Joedy McCreary in Durham, North Carolina; and Charles Odum in Atlanta; contributed to this report.

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Follow Aaron Beard on Twitter at http://www.twitter.com/aaronbeardap