The NFL regular season moves at an absolutely relentless pace.

Early in the year, it’s easy to dismiss what we have seen so far based on the idea that it’s just a small sample size.

But that’s missing the point.

The truth is that the entire NFL season is a small sample size.

After all, it is a 16-game season.

That small sample size means we can expect the unexpected – a sort of predictable unpredictability in a way.

As we hit the quarter mark of the 2019 regular season, it makes sense to reflect on how drastically so many perceptions have changed over just four weeks.

Think about this.

Less than a month ago, NFL fans overseas with tickets to this Sunday’s game at Tottenham Hotspur Stadium anticipated seeing Antonio Brown and the Oakland Raiders clash with Mitch Trubisky’s Chicago Bears.

Brown is out of the league following a brief stop with the New England Patriots.

Trubisky won’t play because of a dislocated left shoulder.

I’m not sure what the odds are that anybody in London bought a ticket to see Vontaze Burfict play this weekend but if they did, well, you get the point.

The bad news for the Raiders is that Khalil Mack is among the players that will play in London this weekend.

Mack, who has recorded 4.5 sacks and three forced fumbles over his past three games, will have had this game circled on his calendar since it was first announced.

And it isn’t because he is looking forward to tea with Raiders QB Derek Carr.

Chicago’s stingy defence has allowed an NFC-best 11.3 points per game this season.

With Trubisky sidelined, it will be on the veteran Chase Daniel to guide the Bears to victory in London.

It’s a small sample size, but Daniel is just one name on a growing list of replacement quarterbacks that earned wins in their season debuts.

Kyle Allen has led the Carolina Panthers to consecutive victories with Cam Newton sidelined.

In Week 5, he’ll go head-to-head with another replacement quarterback that has rallied his team to .500 in rookie sixth-round pick Gardner Minshew II.

Minshew owns the highest passer rating of any rookie quarterback through their first four games in the Super Bowl era.

Allen is just the third quarterback in the Super Bowl era to win his first three career starts on the road, joining Jeff Hostletler and Patrick Mahomes III.

It’s a small sample size, but barring a tie one of those quarterbacks will improve to 3-0 this weekend.

What will happen when Newton and Nick Foles are healthy again?

For now, let’s just enjoy the ride.

Matt Barkley could also join the list of replacement quarterbacks to start this season when the Buffalo Bills visit the Tennessee Titans on Sunday.

Josh Allen is in concussion protocol after he was knocked out in a 16-10 loss to the New England Patriots.

Our NFL analyst Davis Sanchez discussed the hit after the game.

While Bills fans have every right to be frustrated by an injury to their starting quarterback, it’s becoming quite clear who the two most important players on any NFL roster are.

The most important player is the starting quarterback.

The second-most important player is the backup quarterback.

It’s only Week 5, but the list of starters for this Sunday will include Barkley, Allen, Minshew, Daniel, Teddy Bridgewater, Mason Rudolph, Josh Rosen, Luke Falk, Jacoby Brissett and Daniel Jones.

Almost one third of NFL teams have made a switch, either by choice or otherwise, before the quarter mark of the regular season.

If nothing else, it adds even more uncertainty to an already small sample size.

The changes at the game’s most important position have resulted in a couple of early-season trends.

First, the average age of starting quarterbacks has declined, with more young passers getting an opportunity.

Second, for the most part those young quarterbacks have delivered.

In Week 4 alone, 11 of the 15 winners had starting quarterbacks who are 26-years-old or younger.

Passers that are 26 or younger have combined for an NFL-record 39 wins through the first four weeks of the season – eight more than the previous record, which was set in 1987.

Four games might not be a big enough sample size to predict a Super Bowl winner.

However, it’s more than enough to cross a number of teams off the list of potential playoff teams.

The Miami Dolphins, Cincinnati Bengals, Denver Broncos and Washington Redskins have posted a combined 0-16 record.

It’s safe to say that none of those teams will make the postseason.

Then you have the Arizona Cardinals and New York Jets, which are a combined 0-6-1 this season.

We can feel confident crossing them off the list as well.

That leaves 26 of the 32 NFL teams to compete for playoff spots, which might even be generous considering it means not writing off either the Atlanta Falcons or the Pittsburgh Steelers just yet despite 1-3 starts.

It might be a small sample size, but that’s the point.

In the NFL, you are what your record is.

All we can do is guess what happens next.