After an extremely tight regular season, the O'ahu Interscholastic Association Red Conference playoffs begin this weekend with two first-round games.

West Division No. 5 seed 'Aiea (3-5) travels to East No. 4 Castle (3-5) at 6:30 tonight, and East No. 5 Kailua (4-4) faces West No. 4 Kapolei (3-5) at 7 p.m. tomorrow at Mililani Stadium.

Both games will be televised live statewide on OC-16.

None of the 14 teams in the OIA Red Conference made it through the regular season undefeated, and the two No. 1 seeds — Kahuku in the East and Wai'anae in the West — lost to teams that finished third and fourth in their divisions.

The top three teams in each division received first-round byes and will begin playoff action in next week's quarterfinals.

Also, another big showdown looms in the Interscholastic League of Honolulu as unbeaten Saint Louis, ranked No. 1 in The Advertiser's statewide Top 10 poll of coaches and media, takes on No. 4 Kamehameha tonight at Aloha Stadium. Kickoff is set for 7:30, following the Division II matchup between 'Iolani and Pac-Five at 4:45 p.m.

Here is a closer look at this weekend's key games:

'AIEA AT CASTLE

Last week: 'Aiea had a bye; Castle lost to Farrington, 32-22

Notable: This is a rematch of last year's quarterfinal game won by 'Aiea, 52-31. That game was at Kaiser, but this time the Knights have home-field advantage. There will be extra emotion on the Castle side since the Knights have been preparing for the Saturday funeral of teammate Patrick Kapahu, a starting offensive/defensive lineman/punter who died two weeks ago after suffering head injuries in a skateboarding accident. ... Each team has a tough, productive quarterback. 'Aiea's Alfredo Higa has completed 130 passes in 230 attempts (56.5 percent) for 1,561 yards (third in the state) and 13 touchdowns. Receiver Lofa Li'ili'i (38 catches, 507 yards, 3 TDs) is one of the state's top all-purpose threats. He returned a punt 85 yards for a touchdown in the regular season finale, a 24-20 loss to Leilehua. ... Castle's Bryson Ukauka, meanwhile, has thrown for 1,049 yards and seven TDs. He is particularly dangerous on deep routes, having hit Scott Keiter-Charles on touchdown passes of 80 and 72 yards. The Knights' Corey Paredes is a standout two-way performer, a hard-hitting ball hawk at linebacker and a dependable receiver on offense (eight catches, 109 yards vs. Farrington).

KAMEHAMEHA VS. SAINT LOUIS

Records: Kamehameha 6-2 overall, 2-2 in the ILH; Saint Louis 7-0, 4-0

Last week: Kamehameha defeated Pac-Five, 28-15; Saint Louis defeated Punahou, 33-27

Notable: Saint Louis can clinch at least a tie for first place in the ILH regular season with a victory. A Kamehameha loss eliminates the Warriors from title contention. ... The Crusaders won the first meeting, 10-3, on Sept. 15 after quarterback Micah Mamiya scored on an 11-yard touchdown run with 6:14 remaining. Saint Louis limited Kamehameha's powerful running attack to just 25 yards on 34 attempts. Crusaders defensive end Scott Smith, who stands at 6 feet 7, is solid against the run and forces adjustments by quarterbacks trying to throw over him. ... Mamiya has been extremely efficient running Saint Louis' hybrid "Run and Shoot/Utah" offense, mixing up option runs with read-and-react pass plays. He kept Punahou guessing last week, completing 11-of-21 passes for 141 yards and three TDs, and rushing for 106 yards on 14 carries. ... Kamehameha got a scare last week, as Pac-Five took leads of 9-0 in the first half and 15-14 late in the third quarter. The Warriors' Truman Chun rushed for 105 yards and three touchdowns in the win.

KAILUA VS. KAPOLEI

Last week: Kailua had a bye; Kapolei defeated Wai'anae, 17-13

Notable: Kapolei broke out its special teal jerseys for last week's home finale, and coach Darren Hernandez said the Hurricanes have never lost a varsity game when wearing that color in the five seasons of the program's existence. "We normally wear black for home games, but once in a while we bring out the teal," Hernandez said. "It's good luck for us, like when Notre Dame wears their green." They will wear teal again tomorrow. ... Hernandez credited his defense — led by middle linebacker Justin Cossy, outside linebacker Alvin Julaton, safety Kamuela Foki and defensive backs Kalae Parish, Cyril Ontai and Austin Healy — for bending but not breaking against Wai'anae and forcing three turnovers. ... Kailua was missing three starters in a crucial 21-14 loss to Castle due to disciplinary action. But all three have been reinstated, coach Gary Rosolowich said. ... Kapolei has an effective option attack, but Kailua did well against the run in wins over Damien and McKinley.

Reach Wes Nakama at wnakama@honoluluadvertiser.com.