There’s no sibling rivalry between Charter Oak sophomore pitcher Leila Diebert and junior outfielder Mikayla Diebert.

They seem like each other’s biggest fan, and together they have helped turn the Chargers program into a juggernaut the past two seasons.

“It’s really nice getting to watch her pitch, grow up and fight her own battles,” Mikayla said of Leila, who has a 0.76 ERA with 90 strikeouts in 55 innings. She can hit too, batting .438 with 15 RBIs, six home runs and six doubles.

Mikayla is just as dangerous at the plate, batting .583 with 19 RBIs, seven doubles and a home run.

“I look up to her,” Leila said of Mikayla. “We’re going to stick together until she goes to college or I got to college. We grew up doing this and we’re having a lot of fun right now.”

When Charter Oak’s softball team defeated West Covina 14-4 on Wednesday it capped a perfect 16-0 regular season. It will be the only undefeated team in the CIF Southern Section playoffs when the pairings are announced Monday.

You have to go way back in the archives to find another Charter Oak softball team that entered the playoffs with an undefeated record.

It has happened only one other time, and that was one of the top teams in San Gabriel Valley history.

In 1993, pitcher Christy Tucker led Charter Oak to a 29-0-1 season that included a 3-1 victory over Bishop Amat in the CIF-SS Division II title game. It was arguably one of the best teams in SGV history, and Tucker went on to pitch at Long Beach State. It was the Chargers’ third section title, having also won in 1979 and 1990.

While Charter Oak is having a special season, having a similar outcome as the 1993 team and winning its first title in 32 years feels like one of those improbable longshots.

Why a longshot?

This is the first year that the CIF-SS is using computer rankings to determine where to place teams in the playoffs. The Chargers are No. 6 in this week’s rankings, which makes them a sure thing to land in the ultra-tough Division 1 playoff bracket for only the second time in school history.

In 2015, the Chargers competed in Division 1 and lost in the first round to Valencia.

Last season, Charter Oak, boosted by the impact of the Dieberts and a strong supporting cast, reached the CIF-SS Division 3 quarterfinals and finished 19-3-1.

Division 1 will be a major leap forward for the Chargers, and the circumstances have not been ideal for such a dramatic jump.

Stacy Natividad resigned as the team’s coach a week before the season started. The Chargers were able to scramble and bring on Bre Gilchrist to take over, but they weren’t able to put together much of a nonleague schedule, which is why they have played only 16 games.

They did not play in any tournaments and weren’t able to play the type of quality opponents they will likely meet in the playoffs.

Charter Oak’s two best quality wins came over El Dorado (4-3), which is No. 59 in the CIF-SS computer rankings, and Downey (4-3), ranked No. 61. The Chargers breezed through the Valle Vista League and outscored their opponents 177-20.

So, they’re good, but how good?

“I think it’s a little surprising for us that we get to compete at the D1 level,” Mikayla said, “but we’re not nervous about it, it’s a great opportunity. We get a chance to showcase the talent around our whole program. We didn’t graduate anyone from last year’s team. We’ve got an amazing group that stuck together. An amazing group of seniors that lead us. We want to show not only our school, but our community, what we’re all about.”

Leila knows that as a pitcher, she will be facing lineups that are tough from top to bottom.

“I would say the biggest adjustment is having to hit my spots and be more accurate,” Leila said. “Need more spin and more movement, just have to go out there and compete.

“I wouldn’t say it’s a nervous feeling competing in Division 1. A lot of us have played this type of competition in travel ball. It’s a big opportunity for us and very exciting to see how we can do. We have a lot of good players on this team.”

The Chargers have several seniors to lean on. Jazmyn Johnson has been clutch at the plate, batting .423 with 15 RBIs. Lyla Caston brings a lot of power. She’s hitting .423 with 24 RBIs and six home runs.

Senior Alyssa Lopez does it all too, batting .514 with 23 RBIs. Jayla Brown had two home runs, two doubles and two RBIs in Wednesday’s win over West Covina. She’s batting .421 with 15 RBIs and three homers.

There is also senior pitcher Mibella Huerta, who gives them a solid one-two punch in the circle. Huerta has a 1.20 ERA in 41 innings with 45 strikeouts.

They have pitching, power and experience. But so too will so many others in Division 1.

“Whatever happens, I love our team,” Mikayla said, “love how we supported each other during the coaching change and put together this great season. I think we’re ready with whatever gets thrown at us. And if we get thrown into a tough situation, I think we’ll be able to fight together to get out of it.”