Coming into the week, the Corona del Mar High girls’ tennis team had lost just once all season, a nonleague match at Palos Verdes in September.

CdM welcomed another opponent from the Bay League, Mira Costa, to its courts on Wednesday afternoon in the semifinals of the CIF Southern Section Division 1 playoffs.

A rough start led to a rally, but the result was the same.

Mira Costa upset top-seeded Corona del Mar 11-7, ending the Sea Kings’ hopes of a repeat CIF championship in the top division.

The Mustangs (19-2) won six doubles sets, advancing to Thursday’s Division 1 title match, which was moved up a day due to rain in Friday’s forecast. Portola beat Mira Costa 10-8 for the crown at the University of Redlands.

The season isn’t over for CdM, which will compete in the CIF/USTA Southern California Regionals beginning Nov. 20 at the Claremont Club.

Sunset League champion CdM (15-2) fell behind 5-1 after the first round in the semifinal match and could never quite get all the way back against Mira Costa, which shared its league title with Palos Verdes.

“It was a tough match; they’re good,” CdM singles player Sienna Lynn said. “Obviously, the first round didn’t go like we wanted it to … but I think we competed well as a team. It’s tough. They brought 10 extra subs, so you hear a lot more noise coming from their side. Then, you win a point, and it’s way quieter. But I think we competed, despite that fact.”

Mira Costa senior Eva Lansky saved a set point in edging CdM’s Brynn Patterson 7-6 (7-4) in the first round, helping the visitors earn the sizable lead.

“It was definitely hard mentally, because [Patterson] was very confident in herself,” Lansky said. “She was yelling a lot, and I’m more of a quiet player. It was hard for me to keep myself calm. Mentally, I was struggling, I’m not going to lie … but I tried my best to stay calm and just play my game.”

Mia Sandblom swept, 6-0, 6-0, 6-4 at No. 1 singles for the winners, with Lynn pushing her the most. Lansky and Sienna Chun each won once. Julia Cross and Lynn each won twice for CdM.

CdM could muster just three doubles sets, two of those by Ruby Jacobs and Soraya Burwell. Olivia Lew and Gigi French won the other set.

Each of Mira Costa’s doubles teams — Ava Rastegar-Panah and Sofie Rolland, Calista Chun and Alison Ho, and Chloe Stephens and Laken Ashcroft — won twice.

“Doubles was tough today,” CdM coach Jamie Gresh said. “They were just all over the net, way more active in doubles. That’s why they won six [sets] and we won three … Mira Costa is definitely a deeper team, and it showed.”

Corona del Mar rallied within 7-5 after two rounds. But, with Mira Costa having a sizable games lead thanks in part to Sandblom, the match was all but clinched for the Mustangs.

It has still been a season of accomplishment for CdM, which lost six starters from last year’s state runner-up team. This year, the Sea Kings will graduate just one senior starter, French, so they should be among the section’s top teams in 2027 as well.

“We’re a pretty new team, new dynamic and everything, but I think we’re all going to become a lot better next year,” Lynn said.