Starting at next weekend’s Quaker State 400 in Atlanta, the NASCAR Cup Series will be following the lead of other sports leagues — from European soccer to the NBA — by launching its own in-season tournament to spice up the regular-season schedule.

Seeding for the inaugural In-Season Challenge came from a three-race stretch (Michigan, Mexico City and Pocono), using a mix of highest finishes and points earned. Now, 32 drivers are locked into one big single-elimination bracket, ready to square off head-to-head until one is crowned champion — and handed a $1 million check.

Whether you’re a weekly watcher or a casual fan, this guide will help you get up to speed on the bracket, the favorites and long shots, and the winners or losers of the seeding process. To help us along the way, we also dusted off a retooled version of my Cup Series playoffs forecast model, which uses each driver’s track type-specific projected ratings to simulate the tournament 2,000 times and estimate each driver’s odds of advancing.

Here are the current favorites:

With the bracket and odds in hand, let’s take a closer look at how the field shapes up:

The favorites

Despite being seeded just 18th in the wake of uncharacteristically low finishes in two of three qualifying races, William Byron has been the best driver in Cup racing this season — he’s No. 1 in the standings and in average Driver Rating — and that makes him the biggest threat to win here.

The two-time defending Daytona 500 winner will get a favorable first-round matchup against Ryan Preece (a good but not great superspeedway guy), potentially be slotted against much less consistent road course drivers in both Round 2 (Chase Briscoe) and Round 3 (Kyle Larson), and would face a lesser oval driver (Chris Buescher) in the Championship 4 if things came down to that. Byron ought to be favored at each step until the championship.

Of course, chaos reigns at drafting-style tracks, so being the favorite is hardly a guarantee, right from the get-go. If we look deeper into the field, 5% or better odds also belong to Christopher Bell, Denny Hamlin, Chase Elliott, Briscoe, Buescher and Larson. (Plus Ryan Blaney and Joey Logano if we want to round the percentages up to the nearest whole number.) Of those, No. 1 Hamlin and No. 5 Elliott have the best chances to make the Sweet 16, having drawn lopsided first-round matchups with the Dillon Bros. — No. 32 Ty and No. 28 Austin, respectively.

Elliott also has the best chance to make the Elite 8, as he would face either John Hunter Nemechek or Josh Berry, neither of whom is good on road courses, in Round 2.

The Cinderellas

If we consider Byron a “Cinderella” by virtue of his bottom-half seed number, he has by far the best odds to make and/or win the championship round of any driver in that category. But it feels odd to call the No. 1 ranked driver in standings a long shot.

Similarly, Logano and Tyler Reddick have the next-best odds of that group, but the former is the defending Cup Series champ and the latter was in last year’s Championship 4; neither would really shock with a deep run, even though Reddick would have to go through Larson and then (most likely) Blaney right away.

Conversely, could we consider Ty Gibbs a sleeper pick? He’s 23rd in the main standings… but he’s also the No. 6 seed in the In-Season Challenge bracket, and his performance has been ticking up lately (after we graded his season a “D+” at the All-Star race last month). Winnable matchups with No. 27 Justin Haley and No. 11 Michael McDowell could very well land Gibbs in the Round of 8, which would feel both expected (given his seed) and surprising (given his level of performance during the season to date).

If we limit things to drivers who are currently 15th or lower in both the Challenge seeding and the regular standings, four drivers have a 10% chance or better to win at least two rounds: No. 19 Austin Cindric, No. 22 A.J. Allmendinger, No. 16 Kyle Busch and No. 17 Brad Keselowski. All are known as aces at either drafting-type tracks or road courses (or in the case of Cindric, both), and those tracks make up each of the first three races in this tournament.

Longtime championship rivals Busch and Keselowski can’t both make deep runs — they face each other in Round 1 — but the winner would likely catch Hamlin at a road course (where he hasn’t been elite during the Next Gen car era), while Cindric and Allmendinger would be on a potential collision course at Sonoma in the Round of 8.

The spoilers

Sometimes it’s not about winning the title as much as it’s about being a thorn in the side of the favorites. In this bracket, that might be the case for Keselowski, Reddick, Erik Jones and Carson Hocevar — each of whom has at least a 44% chance to knock off drivers who are both better-seeded here and more highly ranked in the 2025 Cup standings.

We already mentioned Brad K’s battle with Busch (that one’s a virtual toss-up between seeds 16-17), but Reddick is a solid plate racer with a real chance to end Larson’s run immediately, while there’s a roughly 50% chance that either Jones or Hocevar upset Ross Chastain or Blaney, respectively, and nearly a 21% chance that both move on.

Looking further ahead, we could see Logano giving trouble to No. 9 Bubba Wallace in the second round if Joey survives Alex Bowman in Round 1, as Bubba is not a strong road course driver. Also, McDowell would nearly be a coin-flip to defeat Gibbs in a Round 2 fight between drivers who have shown an aptitude for making left and right turns during their careers.

And if we ignore the seeds for a moment, Briscoe does have the potential to turn Byron from the favorite to an afterthought if he gets a good run on the streets of Chicago. Briscoe ran well with a 96.3 Driver Rating at the last road course race, at Mexico City a few weeks ago.

The tough draws

In contrast with the spoilers, some good drivers just landed in a bad spot thanks to the seeding formula. Preece might be exhibit A — he’s been having a breakout season, but he ended up in the No. 15 slot while Byron’s 27th-place finish at Pocono dropped him to No. 18, directly in Preece’s path. The underdog could still win, since Atlanta is a comparatively chaotic track now, but it’s a rough thing to start the In-Season Challenge off against the standings leader.

Bowman fits that mold as well: He’s seeded eighth, which matches with the No. 25 in a 32-driver bracket. But unfortunately for him, that means facing Logano at a place where Joey won in last year’s playoffs and is always a threat. If Bowman wins, he would get his own favorable draw against No. 9 Wallace as a much better road course driver in Round 2, but he has to get through Round 1 first.

Then there’s just the way the seeds can lie about the relative quality of the drivers. Zane Smith is seeded 14th, but he would be an underdog most anywhere against No. 19 Cindric — particularly at Atlanta, where Cindric had a streak of five straight races finishing 12th or better from 2022-2024. Similarly, No. 12 Nemechek got No. 21 Berry in Round 1, a seeding anomaly that isn’t really reflective of how they’ve been doing all season long.

And while they’re all still favorites to advance past Round 1, the trio of Chastain, Blaney and Larson may not have it as easy as we might think at a glance. For Ross, that’s because drafting tracks are a clear weakness in his driving portfolio, setting him up on comparatively shaky ground right away in his matchup against Jones.

And for Blaney and Larson, their respective first-round opponents — Hocevar and Reddick — are tougher than the rest of the Top 10 (save for Bowman) have to face. Not only that, but even if both favorites win, Blaney and Larson will then have to face each other in Round 2, quite possibly for the right to face Byron in Round 3.

And maybe that’s the point. In this format, even the big names aren’t guaranteed more than a single race in contention before the bracket starts scrambling everything up. With its chaotic seeding and track types, as well as the inherent unpredictability of single-elimination racing, this new In-Season Challenge promises to be as wild and experimental as anything NASCAR has tried in years — which is really saying something for this sport.