Mater Dei and Fairmont Prep’s girls basketball teams seemed destined for the CIF-SS Open Division playoffs. Sage Hill, however, teetered on the proverbial bumble entering Saturday’s release of the first postseason pairings guided by computer-generated ratings.

The Lightning are headed back to the Open for a third consecutive season.

Positioned ninth in the section’s computer ratings earlier in the week, Sage Hill (19-8) received the eighth and final spot in the premier division. The Lightning begin Pool A at top-seeded Ontario Christian (25-1) — ranked No. 1 in the nation by MaxPreps — on Saturday.

“There is a lot of mix(ed) messages going on (as) we are eighth in all of Southern Section but rate fourth (in) Orange County (by OCVarsity),” said Sage Hill coach Kerwin Walters, whose team slipped in the county rankings after a loss against Rialto on Feb. 1 while short-handed. “(I’m) not really sure how to make sense of this but we never back down from a challenge.”

In the Rialto game, Sage Hill lost starting freshman guard Addison Uphoff to a season-ending foot fracture, Walters said.

The Lightning’s final power-rating was 2.76, which edged Ventura (2.66) for the eighth spot.

Mater Dei (26-2) posted the highest strength of schedule for top teams in the state according to MaxPreps, but slipped behind reigning state champion Etiwanda (22-4) for the No. 3 seed. That’s an important seeding because Etiwanda will be the host team when the teams collide in their final Pool B game on Feb. 22.

First-year Mater Dei coach Jody Wynn said her team is excited to compete in the “toughest playoff division in the nation” but said the Monarchs wanted the No. 2 seed that went to Etiwanda.

“We are definitely disappointed that we didn’t receive the No. 2 seed,” she said. “We feel our girls earned it through our incredible strength of schedule and overall record.”

The Feb. 22 clash could potentially be a semifinal but the Monarchs also need to first navigate home games against No. 6 Windward on Saturday and No. 7 Fairmont Prep on Feb. 19. Mater Dei recently lost standout junior Kaeli Wynn — the coach’s daughter — to a season-ending knee injury.

Fairmont Prep (20-8), which reached the Open Division for the first time since 2017, opens at Etiwanda on Saturday.

Division 1 includes six other teams ranked in the county Top 10, including a pairing Thursday between O.C. No. 8 Orange Lutheran (13-11) and host No. 7 Crean Lutheran (22-5).

San Clemente (23-5), which has climbed to No. 2 in the county rankings, opens Division 1 against visiting Valencia of Valencia (25-4) on Thursday. If the Tritons win, they’ll face the winner of the Bonita at JSerra game in the second round.

Buena Park (20-6), ranked No. 10 in Orange County, earned the top-seed in Division 2AA and an intriguing first-round pairing with St. Joseph of Lakewood (22-4) on Thursday. St. Joseph features former Buena Park standouts Bella Harmon and Alana White.

“Business as usual,” Buena Park coach DeAnthony Wiley said of the matchup. “We approach every game with the same mentality and focus.”

Division 2A will feature No. 4 seed Fountain Valley, Corona del Mar, Los Alamitos and Marina, the top four teams from the tightly-contested Sunset League. Rosary is seeded second.

In a show of the county’s depth, Pacifica Christian (3AA), Savanna (4AA) and Loara (5AA) each earned top seeds.