Sam Mayer claimed his first career NASCAR Xfinity Series oval-race victory in the second half of a NASCAR double-header at Homestead-Miami Speedway on Saturday in the Contender Boats 300 after holding off last week’s race winner Riley Herbst by a mere .227-second.

It marks the JR Motorsports driver Mayer’s fourth series victory of the season – and his career – most important for Mayer – who joked he didn’t breath the final four laps – it is his ticket into the Championship 4 finale that will decide the series title at Phoenix Raceway in two weeks.

The 20-year old Wisconsin native’s No. 1 JR Motorsports Chevrolet led 46 laps on the day – including the final 30 – but brushed the wall exiting Turn 3 as he pushed forward on the last lap to keep a fast-closing Herbst behind him. Mayer’s fellow NASCAR Xfinity Series championship contender John Hunter Nemechek finished third in the No. 20 Joe Gibbs Racing Toyota; leading seven laps despite feeling under the weather.

Regular-season champion Austin Hill was fourth in the No. 21 Richard Childress Racing Chevrolet and NASCAR Hall of Famer and crowd favorite, Dale Earnhardt Jr. finished fifth in his second and final race start of the season. He’s also the owner of Mayer’s Chevy.

“It’s unreal, we won on an oval,’’ a grinning Mayer screamed into the front grandstands. “This Chevrolet Camaro was so good.

“It’s all about putting a full race together,’’ he continued, “and I’m so proud of these guys. They kicked tail on pit road and we made it happen with these HMS (Hendrick Motorsports) engines.

“It’s just really cool to be able to beat an amazing organization like that (Herbst’s Stewart-Haas Racing team). We’ve got to turn it on a little harder going into Phoenix.’’

Herbst’s Stewart-Haas Racing teammate Cole Custer won Stage 1 and led a dominating 114 of the race’s 200 laps only to suffer a tire problem with 50 laps remaining and drop a lap down. He rallied back but still finished 13th after such an impressive early race. Custer and Hill are now tied three points above the cutoff line heading into next week’s regular season finale at the half-mile Martinsville (Va.) Speedway. Nemechek holds a healthy 44 point edge above them.

Another title favorite, Mayer’s JRM teammate Justin Allgaier – who came into the race ranked second in the championship standings, also had a tire issue after a pit stop and dropped back midway through the race. He rallied back to finish 15th, but dropped to fifth place in the standing, three points behind Hill for the automatic transfer position for the Championship 4.

Nemechek’s JGR teammate Sammy Smith, who finished ninth, is now 49 points back in sixth place. And it was a more dramatic day for the other championship contenders with Richard Childress Racing’s Sheldon Creed finishing 26th after exiting onto pit road with smoke trailing out of his Chevy with only two laps remaining in the race.

Kaulig Racing’s Chandler Smith rounds out the Playoff 8 – but finished a frustrating 34th place after being collected in an early race accident. They are now 54 (Smith) and 65 (Creed) points below the fourth place transfer line and will need to win the race at Martinsville next week to meet their Playoff goals.

Kaulig’s Daniel Hemric, Big Machine Racing’s Parker Kligerman, JRM’s Brandon Jones, and the Joe Gibbs Racing teammates Sammy Smith, and Joe Graf Jr. rounded out the top 10 Saturday.

Earnhardt’s participation was certainly a crowd pleaser and his fifth-place effort in the JR Motorsports Chevy was his fifth top-five showing since he retired from fulltime competition in the NASCAR Cup Series after the 2017 season. He methodically worked his way forward from a 23rd place starting position and survived a close call in the closing laps, ironically with Josh Berry, who drives for Earnhardt.

“Luckily it didn’t hurt our car and we were able to finish really good, so I’m happy about that,’’ Earnhardt said, noting he felt badly having an incident with one of his own team cars.

The series moves to the half-mile Martinsville (Va.) Raceway for next Saturday’s Dead On Tools 250 (3:30 p.m. ET, USA Network, MRN, SiriusXM NASCAR Radio) which will formally decide which three drivers will join Mayer in championship eligibility at the Phoenix season-ender.

“Getting that first oval win [today] was big. … we finally won on an oval and my confidence is feeling good,’’ Mayer said with a huge grin.