The Thames River Crusaders will play their first playoff game in program history at home in Tuesday’s CIAC quarterfinals.

Ledyard lost its opportunity to do the same.

Valley Regional/Old Lyme, meanwhile, is headed to Milford.

Thames River is seeded fourth in Class MM and will host No. 5 North Haven at Grasso Tech.

Ledyard is seeded eighth in Class SS and will play top-seeded Cromwell/Portland at Pierson Field in Cromwell.

Valley/Old Lyme is sixth in Class SS and will play at No. 3 Foran.

All quarterfinals are Tuesday at the higher seed.

Seeding for all six playoff divisions won’t officially be finalized until the CIAC football committee gives its stamp of approval on Friday. All games are scheduled to start at 6:30 p.m.

Thames (10-0) is one of just five unbeaten teams in the state. The cooperative ,which plays at Grasso Tech and also includes Norwich Tech and St. Bernard, was fifth in the Class MM rankings heading into Thanksgiving week.

The Crusaders moved up to fourth after Newington upset Wethersfield on Wednesday night, 17-14. They finished the regular season second in the state in scoring (485 points) and first in points allowed (19). They had seven shutouts, putting them in a 13th-place tie for most in a season, according to the Connecticut High School Football Record Book. They’re just the seventh team to do it in a 10-game regular season.

North Haven (8-2) plays out of the Southern Connecticut Conference’s Tier 1, one of the state’s toughest divisions with five of its seven teams qualifying for the postseason. The Nighthawks own wins over Class L participants Shelton (18-10, Sept. 30) and Cheshire (10-0, Oct. 28).

Ledyard (8-2) would have hosted a home quarterfinal in Class SS, but rival Fitch ended that hope with a 46-36 win on Thursday morning.

Cromwell/Portland (9-1) was last season’s Class S champion and is the Pequot Football Conference Sassacus Division champion.

Valley/Old Lyme (9-1) earned a berth when Cromwell/Portland routed Rocky Hill on Wednesday night, 38-7.

Cromwell/Portland, oddly enough, was the one team that managed to beat Valley/Old Lyme (28-27, Oct. 28).

Foran (9-1) would have been the top seed in Class SS had it not been thrashed by town rival Law on Thursday, 60-29.

Killingly and Windham join Ledyard as the Eastern Connecticut Conference’s other playoff representatives.

Killingly (9-1), last season’s Class M champion, is seeded third in Class MM. It will host No. 6 Wethersfield (8-2).

Windham (9-1) is No. 2 in Class SS and will play No. 7 Gilbert/Northwestern/Housatonic (8-2). The game will likely be played at E.O. Smith in Storrs because Windham’s athletic complex has been undergoing a complete renovation.

The unofficial pairings are as follows:

Class LL: No. 1 Southington (9-1) vs. No. 8 Trumbull (7-3); No. 2 Greenwich (8-2) vs. No. 7 Hamden (8-2); No. 3 West Haven (9-1) vs. No. 6 Glastonbury (8-2); No. 4 Staples (9-1) vs. No. 5 Fairfield Prep (7-3).

Class L: No. 1 St. Joseph (9-1) vs. No. 8 Cheshire (6-4); No. 2 Newtown (9-1) vs. No. 7 Shelton (6-4); No. 3 Maloney (9-1) vs. No. 6 New Milford (7-3); No. 4 New Canaan (9-1) vs. No. 5 Naugatuck (8-2).

Class MM: No. 1 Sport and Medical Sciences Academy co-op (10-0) vs. No. 8 Wilton (7-3); No. 2 Northwest United (10-0) vs. No. 7 Masuk (7-3); No. 3 Killingly vs. No. 6 Wethersfield; No. 4 Thames River vs. No. 5 North Haven.

Class M: No. 1 Berlin (10-0) vs. No. 8 Branford (5-5); No. 2 Notre Dame-West Haven (7-3) vs. No. 7 Hartford Public (6-4); No. 3 Law (9-1) vs. No. 6 RHAM (7-3); No. 4 Rockville (8-2) vs. No. 5 Abbott Tech/Immaculate (8-2).

Class SS: No. 1 Cromwell/Portland vs. No. 8 Ledyard; No. 2 Windham vs. No. 7 Gilbert/Northwestern/Housatonic; No. 3 Foran vs. No. 6 Valley/Old Lyme; No. 4 Granby/Canton (8-2) vs. No. 5 Barlow (8-2).

Class S: No. 1 Ansonia (10-0) vs. No. 8 North Branford (6-4); No. 2 Bloomfield (8-2) vs. No. 7 Seymour (6-4); No. 3 Holy Cross (8-2) vs. No. 6 New Fairfield (7-3); No. 4 Woodland (8-2) vs. No. 5 East Catholic (7-3).

n.griffen@theday.com