Who was that?! Unheralded ballers who mattered in Week 16

Sometimes the NFL's top plays on a Sunday come from people we wouldn't expect. They're the plays that make you ask, "Who was that?" These performances can change a player's career.

Here's a look at Week 16's unheralded ballers, starting with a pair of replacement linebackers who helped the Patriots and Rams clinch something special.

Marquis Flowers, LB, New England Patriots

Team-high 10 tackles, 2.5 sacks in 37-16 win over Bills

What happened: Flowers' biggest play came on a fourth-and-2 tackle of Tyrod Taylor as he scrambled to the right sideline. It was a huge turnover on downs.

Why it matters: The Patriots are thin at linebacker, but Flowers showed up in a big way. He didn't have a sack entering the game. He has earned more playing time going into the playoffs. The Patriots clinched a first-round bye.

Cory Littleton, LB, Los Angeles Rams

Interception and sack in 27-23 win over Titans

What happened: Littleton got a great drop into his zone and made a play on the ball when Marcus Mariota tried to throw it over his head. Littleton also took down Mariota later in the game.

Why it matters: Littleton is a backup linebacker more known for his two blocked punts this season, but he stepped up as a defensive playmaker in place of the injured Mark Barron. The Rams clinched the NFC West.

Damiere Byrd, KR/WR, Carolina Panthers

103-yard kick return TD in 22-19 win over Bucs

What happened: Byrd ran up the gut, broke a few tackles and glided along the right sideline for the Panthers' first TD to put them up 12-6.

Why it matters: The Panthers had to claw to a win against the Bucs, and who knows if it would've happened without Byrd's big return. It clinched a playoff spot for Carolina.

Jordan Poyer, FS, Buffalo Bills

Pick-six of Tom Brady in 37-16 loss to Patriots

What happened: Poyer made a great read and jumped a Brady pass for the diving interception. He got up and took it to the house.

Why it matters: There was frustration among the Bills after Poyer didn't get Pro Bowl recognition, but plays like that one on Brady will give you national recognition.

David Morgan, TE, Minnesota Vikings

Emergency long-snapper duties

What happened: Vikings long-snapper Kevin McDermott suffered a shoulder injury, and Morgan stepped up to complete his duties despite never having done so in an NFL game before.

Why it matters: The cliché of "next man up" is challenged when a position has no backup. Morgan shifted over at long-snapper as though it was nothing and provided a much-needed effort as the Vikings fought for a first-round bye.

NFL Nation reporters Mike Reiss and Courtney Cronin contributed to this story.