The Pocono 400 on Sunday officially marks the start of the second half of the Monster Energy NASCAR Cup Series regular season.

After the first 13 races, Kevin Harvick and Kyle Busch have separated themselves as the drivers most likely to end up in victory lane after any given race.

Combined, Harvick (five) and Busch (four) have won nine of the 13 races and both have had winning streaks of three consecutive races.

Last weekend at Charlotte Motor Speedway, Harvick collected a $1 million bonus for winning the All-Star Race on Saturday, but Busch took the Coca-Cola 600 on Sunday.

Still, while Harvick and Busch look like the drivers to beat going into the "Tricky Triangle," it doesn't mean either will win and it certainly does not mean the race for the Monster Energy Cup championship is close to being over.

Kyle Busch won  the NASCAR Cup Series auto race at Charlotte Motor Speedway on Sunday. CHUCK BURTON / AP
Kyle Busch won  the NASCAR Cup Series auto race at Charlotte Motor Speedway on Sunday. CHUCK BURTON / AP

After the Pocono 400, 12 races will remain to determine which 16 drivers will qualify for the playoffs.

That's the sweet spot for the 30 full-time drivers — first, qualify for the playoffs, and then drive in the final 10 races to advance to each stage. A stage is three races, after which four racers with the fewest points are eliminated. The final stage is a one-race shootout between the last four remaining drivers.  Whoever places highest is the champion.

That's a lot of ifs, ands or buts.

Last season, Toyotas won 16 races to take the manufacturers title. This season, Fords have seven wins.

If one crew has a car that is running even slightly better, every other team is working non-stop on how to improve the odds and then sway things in their favor.

"Teams are constantly changing things and trying to make their cars better," said reigning champion Martin Truex Jr. "It's not like you build 10 cars and then just race them all season,

"It's a week-to-week thing where you are constantly changing stuff. You're constantly going into the wind tunnel, working on your engines, and doing all the things you need to do to try to get faster. It's definitely a moving target."

The best team now might not be the best team on Nov. 18 when the final race – Ford EcoBoost 400 – is run at Homestead-Miami Speedway.

The regular season matters because bonus playoff points are gained (5 for a race win, 1 for a stage win). There is a whopping 25 for winning the regular-season championship.

A driver who wins a race during the regular season automatically qualifies for the playoffs. If more than 16 drivers win a race, which is not likely, playoff points will be the tie-breaker.

If the field is not filled by race-winners, playoff points decide the final spots.

Last season, 13 drivers qualified for the playoffs with wins.

So far this season, Harvick, Busch, Truex, Joey Logano, Clint Bowyer, and Austin Dillon have won races.

Having 10 playoff spots available with 13 races remaining sets the stage for some intense racing for wins and/or playoff points the rest of the way.

With so many variables affecting a race, the only thing to expect is the unexpected.