Postseason Football to Kick Off in Big Way : Preps: Largest playoff field ever in Southland begins play tonight.

The largest high school football playoff field ever assembled in the Southland, 200 teams in 13 divisions, begins first-round action tonight. The playoffs last four weeks, concluding with title games Dec. 11-12.

A look at what to expect:

* City Section Division 4-A--Sylmar is one of only two City teams ranked by The Times. The undefeated Spartans also are top-seeded in 4-A, unseating traditional powers Carson, Dorsey and Wilmington Banning. But because Sylmar has not played a team outside the San Fernando Valley this season, there are doubts.

Carson has the most talent but has played erratically for second-year Coach Marty Blankenship. Defending champion Dorsey has talent but lacks a strong quarterback. Banning is coming off back-to-back victories over Carson and Dorsey.

Favorites: Carson and Banning.

Dark horse: Sylmar.

* Division 3-A--Although Bell is top-seeded, San Pedro is the team to beat. The Pirates have lost only to Carson, and have tied Dorsey. Victories over Crenshaw and Banning indicate that the team would be a contender in 4-A as well.

Bell is no longer considered a contender because five of its top players, including the quarterback and a running back, were kicked off the team last week for drinking. San Pedro’s main threats are Woodland Hills Taft and Chatsworth. Taft shut out Chatsworth this season.

Favorite: San Pedro.

Top challengers: Taft and Chatsworth.

* Southern Section Division I--Top-ranked La Puente Bishop Amat is a clear-cut favorite, thanks to its recent victory over Loyola. The undefeated Lancers played one of the toughest schedules in the Southland and had few close calls.

Defending champion Santa Ana Mater Dei has a tough defense but a spotty offense. Loyola, Rialto Eisenhower and Fontana also have stingy defenses but lack the game breaker on offense.

Favorite: Bishop Amat.

Top challengers: Loyola and Fontana.

* Division II--The Southland’s toughest division should be a thriller from the first round to the last. There are 16 solid teams in the bracket, and five are considered strong contenders.

Top-seeded Los Alamitos convincingly defeated Anaheim Esperanza during the regular season, making the Griffins a slight favorite. Rating right behind is Pasadena Muir, whose only loss was to Eisenhower. Undefeated Newhall Hart and Anaheim Servite are threats, and Esperanza cannot be counted out. Hart and Los Alamitos could meet in the semifinals.

Favorite: Los Alamitos.

Top challengers: Muir and Hart.

* Division III--A few weeks ago, La Puente Nogales and Baldwin Park would have been heavy favorites to meet in the championship for the second year in a row. But the Sierra League foes stumbled in the stretch.

Bell Gardens, whose only loss was to Division II power Downey, is top-seeded, but the Lancers will have tough challenges from the quarterfinal round on. Ventura appears to have put its coaching woes behind and has been unbeatable the last three weeks. Hawthorne, Rowland, Santa Barbara San Marcos and Newbury Park will be in the hunt.

Favorite: San Marcos.

Top challengers: Baldwin Park, Hawthorne and Ventura.

* Division IV--Irvine won the Division II title last season, then was moved down to Division IV. The Vaqueros, whose only loss was to Mission Viejo, won the title in the competitive Sea View League and should have little trouble in the playoffs.

Undefeated Riverside Rubidoux is top-seeded, but the Falcons have not played as tough a schedule as many of the Orange Country entrants.

Favorite: Irvine

Top challengers: Rubidoux and Newport Harbor.

* Division V--Top-seeded Indio has not been challenged this season, playing teams mostly from the desert region. The Rajahs, though, will get plenty of competition in the playoffs in a division loaded with contenders.

Alta Loma would have only one loss had it not had to forfeit five games for using an ineligible player. Undefeated Norco, Valley View of Moreno Valley and Temecula Valley are all capable of winning the title.

Favorite: Indio

Top challengers: Norco and Valley View.

* Division VI--Undefeated Covina Charter Oak is the surprise team after going 3-7 last season. The Chargers have outscored their competition, 345-31.

Charter Oak will probably face undefeated Duarte in the championship game. The Falcons are coming off a 48-13 victory over previously undefeated Arroyo. Los Altos, which lost to Charter Oak, 27-14, two weeks ago, is in the opposite bracket and is another title game candidate.

Favorite: Charter Oak

Top challengers: Duarte and Los Altos.

* Division VII--Garden Grove Rancho Alamitos seemed like a clear-cut favorite but then showed its vulnerability by losing to Fountain Valley Los Amigos last week. The Vaqueros, who have one of the top offensive backfields in the area, should bounce back and be a factor.

Fullerton Sunny Hills and Inglewood Morningside are probable title game opponents in an otherwise weak division.

Favorite: Rancho Alamitos.

Top challengers: Sunny Hills and Morningside.

* Division VIII--Top-seeded Riverside La Sierra has won nine in a row since losing its opener to San Dimas. The Eagles’ road to the final, however, is likely to be blocked by Mission Viejo Trabuco Hills, the Division VII runner-up last season.

Pacific Coast League champion Santa Ana Century is only 5-4-1 but handed Trabuco Hills its only defeat.

Favorite: Trabuco Hills.

Top challengers: Century and Yucaipa.

* Division IX--North Torrance had been playing the best ball in the division until it was upset by South Torrance last week. The Saxons received a favorable draw, however, and should have little trouble reaching the title game.

Undefeated Van Nuys Montclair Prep, banished from postseason competition last year for recruiting, is an at-large entrant and should challenge Carpinteria and Nordhoff in the bottom half of the bracket.

Favorite: North Torrance.

Top challengers: Montclair Prep and Carpinteria.

* Division X--Top-seeded Big Bear is known for breezing through the regular season, then stumbling in the playoffs. The undefeated Bears hope to reverse that trend this year.

Traditional power Whittier Christian has rebounded since losing three in a row during the middle of the season. Bishop has won eight in a row since losing its first two.

Favorite: Whittier Christian.

Top challengers: Big Bear and Bishop.

* Division XI--The Southern Section’s newest division has only three leagues, so the playoff field was limited to eight teams.

Undefeated Linfield figures to be challenged by an improved Mammoth and Anza Hamilton.

Favorite: Linfield.

Top challengers: Mammoth and Hamilton.