Gary Landers/Associated Press

There's been a quiet, yet seismic, shift in the NFL that many haven't noticed. But it's there, and it's big, and it has the potential to change the league.

Chiefs tight end Travis Kelce has passed Rob Gronkowski as the best tight end in football.

"[I]t's not even close," one NFC assistant coach told B/R.

This, of course, is debatable, and there are caveats, but across the league, Kelce's play has caught the attention of numerous teams. They say he is elevating the position in a way that Gronkowski did—by using size, speed and athleticism in ways rarely seen at the position.

Plenty of superb and athletic players have manned the position over the decades, such as Tony Gonzalez, Shannon Sharpe, John Mackey, Antonio Gates and Kellen Winslow, to name a few. Then, Gronkowski surpassed them all. Now Kelce is surpassing Gronkowski.

The reason is fairly straightforward, according to former offensive lineman Geoff Schwartz, who's become one of the better NFL analysts around. "Gronk can't stay healthy," Schwartz said. "If both are healthy, Gronk is better. However, Kelce does more within his offense than Gronk does."

David J. Phillip/Associated Press

Video Play Button Videos you might like

Some will say Kelce has always been this good. That's partly true, but watch Kelce on film, as I did this week, and you see a player who, like his quarterback, Alex Smith, is playing at a new level. This is a different Smith and a different Kelce we're seeing now—better than they've ever been before.

Coaches tell me Kelce has sharpened his route running, with more explosiveness than he's shown in the past. Like Gronk, who is 6'6" and 265 pounds, Kelce uses his big frame (6'5", 260) to body defenders. The core dilemma for opponents is that he's too big for a cornerback to cover, and too fast for a linebacker or safety.

Kelce, who is averaging almost six catches per game—a career best—undoubtedly is benefiting from the running of Kareem Hunt, the big-play ability of Tyreek Hill and Smith's sharper performance. But make no mistake: They are also reaping the rewards from playing alongside Kelce.

An important part of that equation, and the Chiefs' 5-0 start, is the fact that Kelce is on the field. Gronkowski's absences are not the sole cause of the Patriots' sluggish opening month, but they're not helping.

Gronk has consistently been one of the most injured superstars in the NFL. I've said for several years that I've never seen an NFL player, in my lifetime, consistently take the kind of massive hits that Gronkowski does every game. The only guy who comes close was former Giants running back Rodney Hampton.

That punishment has taken its toll, though, and slowed Gronkowski. He's still, I've long believed, the best tight end of all time, but that talent isn't of help when he's not on the field.

That isn't to say Kelce is indestructible. Like Gronkowski, we've seen Kelce take some big shots. He was even placed on IR after playing all of one game in 2013. And while he suffered a concussion last week, he is expected to play this Sunday after being a full participant in Thursday's practice.

Jason Behnken/Associated Press

When they are on the field, the beauty of Kelce and Gronkowski are the dual roles they play. Not only can they serve as primary targets, but also reliable escape hatches for their quarterbacks. But an escape hatch that sometimes isn’t there doesn’t offer much of an escape. That isn't Gronk's fault, but it is reality, and in the NFL right now, the reality is that there's not a better tight end playing today than Kelce.

And it may not even be close.

Mike Freeman covers the NFL for Bleacher Report. Follow him on Twitter: @mikefreemanNFL.