Playoff analytics: Most efficient passers, best restarters and fastest teams

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At the halfway mark of the 2021 NASCAR playoffs, 12 challengers remain championship eligible. But coming into today’s Bank of America Roval 400 (2 p.m. ET, NBC), drivers and teams are separated by the magnitude of their statistical strengths.

Let’s take a look at the best and worst of the playoffs in key stat categories:

Most efficient passer: William Byron

Byron teetered on the edge of elimination during the first playoff round and might be in need of a walk-off win today on Charlotte’s Roval to break into the Round of 8. But those notions mask what’s been a sound individual effort in the postseason, one suggesting improvement in his long-run passing acumen across a small sample size.

No driver has a higher surplus passing value* during the playoffs than Byron’s +5.03% mark, from which he’s earned a combined pass differential 68 positions better than a statistical expectation set by his average running position.

Given his average whereabouts in four of the five playoff races were on par with his regular-season average, this is a significant leap over his regular season effort. His SPV after the first 26 races finished in the red, a -0.15% mark, the worst among Hendrick Motorsports’ four drivers.

* Surplus passing value measures the difference in a driver’s adjusted pass efficiency and the expected APE of a driver with the same average running position, based on a field-wide slope.

Least efficient passer: Kevin Harvick

Harvick fares as the least efficient long-run mover among remaining playoff drivers. His -4.81% SPV yielded a combined pass differential 49 positions worse than his statistical expectation and no single race with a positive differential.

Through green-flag pit cycles, crew chief Rodney Childers secured 16 spots worth of track position at Richmond and Las Vegas, supplementing his driver’s long runs well enough to emerge with top-10 finishes in both races.

Best all-around restarters: Martin Truex Jr. and Denny Hamlin

Both Joe Gibbs Racing drivers have put on short run masterclasses during these playoffs.

Truex’s 76% retention rate from inside the first seven rows paces all drivers. He’s one of three drivers with a perfect 100% rate when restarting from the preferred groove specifically. He’s earned 1.64 positions per restart, the second-best average among playoff drivers.

Hamlin, meanwhile, has mitigated typical positional losses on non-preferred groove restarts better than any of his fellow playoff competitors. On 11 such attempts, he’s lost just four positions, beneficial to his playoff-best 17-position net gain. His 75.86% retention rate ranks second, trailing only Truex.

Worst all-around restarter: Kevin Harvick

In addition to his poor output on long runs, Harvick’s short runs — namely, the two-lap windows following each start or restart — are hindering his positional progress.

His 53.33% position retention rate stands as the worst among playoff drivers, as does his 9.09% retention rate from the non-preferred groove specifically.

Fortunately, he seems to be aware of this shortcoming; across 30 choose-rule attempts, he elected to restart from the preferred groove 19 times. Leaning on the strength of each track’s strongest groove has allowed him to minimize a net positional loss (-5 spots) one might expect to be larger given the relative tossup provided by his retention rate.

Fastest team: Denny Hamlin, Joe Gibbs Racing

Hamlin’s Toyota Camry, the fastest car in the playoffs, ranked as the fastest (per its median lap rank) at Richmond and Las Vegas, while his fastest lap in each of the first five playoff races placed within the top four among each driver’s best lap.

It’s a development that’s somewhat surprising but not unexpected. His car ranked as the second fastest overall during the regular season and fastest on 750-horsepower ovals specifically. This initial stretch of playoff races saw three 750-horsepower tracks — key in his success during the run — but producing the fastest car at the 1.5-mile Las Vegas Motor Speedway represented a new, result-shifting wrinkle for 2021 from this No. 11 team.

Hamlin’s fastest outings on 550-horsepower tracks during the regular season came at Kansas and Michigan, races in which his median lap time ranked third.

Slowest team: Alex Bowman, Hendrick Motorsports

It’s been a forgettable playoffs to date for Bowman, in part because he and his team have yet to produce top-five speed on any track, a feat they managed in five of the 26 regular-season contests.

Success in the playoffs, based on speed, was likely to prove difficult for Bowman. He came into the playoffs ranked 10th in median lap time on 550-horsepower tracks and 11th on 750-horsepower ovals, facing a schedule predominantly comprised of his slowest track type.

His fastest car relative to the playoff field came last weekend at Talladega. His median lap ranked eighth in the race and fourth among playoff drivers but didn’t manifest in a windfall of points or a good result. A crash on lap 99 relegated him to a 38th-place finish. He sits 52 points below the cutoff, in need of a win today at the Roval to advance into the Round of 8.

Biggest speed improvement: Kevin Harvick, Stewart-Haas Racing

Harvick’s survival in the playoffs to this point and his potential advancement — he’s nine points below the cutoff in advance of today’s race — are a testament to a team effort, a yearlong turnaround after an early-season struggle. At the conclusion of the regular season, his No. 4 team ranked 11th in average median lap time, sixth on 750-horsepower ovals specifically and 11th on 550-horsepower non-drafting tracks.

In the playoffs, they rank third overall, with his best single-race speed of the entire season coming at Bristol, at which he had the second-fastest car and led 71 laps en route to a runner-up finish. But his 13th-ranked median lap time at Las Vegas might be a sign of things to come in a penultimate round consisting of two similar tracks at Texas and Kansas, if he advances past the Round of 12.

Despite the driver’s foibles and what his team’s speed might deliver him within the next three weeks, it’s been a better, more productive playoff appearance than Harvick or crew chief Childers probably anticipated at its onset.