The playoff bubble.

It's a place where teams with four and five wins reside with one week remaining in the regular season.

Six wins guarantees an invite to the playoff party. Five victories makes a team playoff-eligible, with the caveat of needing a still-to-be-determined number of playoff points to gain entry.

For teams not accustomed to qualifying for the postseason such as Thornwood and Thornridge, the playoff bubble is an exciting place to be.

For teams that have made it a habit to already have qualified for the playoffs such as Mount Carmel and St. Rita, it's a place of discomfort.

Which teams could see their playoff bubble burst?

St. Rita (4-4, 47 playoff points), Mount Carmel (4-4, 43 points), Bremen (4-4, 41 points) and Thornwood (4-4, 36 playoff points) need to win Friday to become playoff eligible. The good news is that history suggests each will receive an invitation to the playoff party based on their current number of playoff points — as long as they win.

St. Rita travels to Marmion (6-2), which has already has stamped its ticket to the postseason. Though Marmion competes in the Catholic League Green, this isn't a walk in the park, St. Rita fans. Marmion beat St. Laurence, which beat St. Rita.

Mustangs coach Todd Kuska is aware of that.

“Marmion is a good football team,” Kuska said. “This is their chance to take down a Catholic League Blue team and possibly secure a home playoff game in the first round. Like I told our guys, our playoffs begin this week.”

Bremen takes on playoff-eligible T.F. South (6-2), which has won six of its last seven.

Thornwood heads to District 205 neighbor Thornridge which, despite its five wins, likely needs to upend the Thunderbirds to reach the playoffs. The Falcons have just 31 playoff points.

Bloom (4-4, 31 points) and Rich East (4-4, 26 points) play one another Saturday — how's that for some Week 9 drama? It's debatable whether either will get in with a win because of a lack of playoff points.

The most intriguing matchup, though, is 12-time state champion Mount Carmel taking on 10-time state champ Providence (3-5).

The Celtics find themselves in a precarious position.

Will Providence, with an eye toward next season, turn to its young, inexperienced players, which would benefit Mount Carmel? Or will the Celtics look to snap the Caravan's 30-year streak of qualifying for the playoffs and play their best 22 players?

“I can see both sides of that argument,” Providence coach Mark Coglianese said. “We'd love to get our juniors some reps. But we're going to play our regulars. We feel like it's still an important game for us. We're not happy we're not in the playoffs. It would be a big win for us to knock them off.”

Who would have imagined the possibility of Providence, Mount Carmel and St. Rita, three Catholic League Blue powers, not qualifying for the playoffs? It's a scenario that could happen.

Coglianese confirmed beating Mount Carmel does produce a downfall.

“We'd like to have as many Catholic League Blue teams in the playoffs as possible,” Coglianese said. “If Marmion beats St. Rita and we beat Mount Carmel, that's three of the better schools in the state not in the playoffs.”

There are a number of local teams with five wins that, because of low playoff points, likely will need to earn a sixth win this weekend.

One of those teams is Shepard (31 points), which should have little trouble reaching six wins with an away game at Argo (1-7).

Ditto Rich Central (28 points), which heads to Alleman (2-6).

However, De La Salle (28 points) has its work cut out against Fenwick (7-1). And though Sandburg (3-5) has struggled, Lincoln-Way West (34 points) can't take the Eagles lightly.

Even if Oak Forest (5-4, 39 points) falls to surging Hillcrest (6-2), the Bengals should have enough playoff points to extend their playoff streak to 17 straight seasons.

“I don't think many people could have predicted how this season has gone,” Coglianese said. “It's been kind of crazy for a lot of teams.”

pdisabato@tribpub.com

Twitter @disabato