Trailing 29-17 at halftime, Althoff used a 14-0 run to climb back in the game and got the winning shot from freshman Brendon Gooch with two seconds remaining Saturday in a 51-49 victory over Mater Dei.
Gooch grabbed the rebound of a missed shot by Ryan Marcum and tossed in the game-winner for the Crusaders (4-2).
Marcum led Althoff with 12 points, while Kevin Renner had nine and Gooch had seven. Zach Haake topped the Knights (1-5) with 11.
"That first half was a little rough," Althoff coach Greg Leib said. "I know we got down 15 or 16 at one time in the third (quarter), but I thought if we could keep it somewhere around the 10 we would still possibly have a chance. That turned out to be the case tonight."
Marcum continues to assert himself as more of a scorer this season for Althoff.
"He's a tough matchup because he can turn and face the basket," Leib said. "He makes those spin moves and his hair's so long it's like a horse mane and it flips those guys in the eyes."
Centralia 61, O'Fallon 45
Todd Porter's 16 points weren't enough as the Panthers (3-3) lost to Centralia.
The Orphans (4-2) forced 20 O'Fallon turnovers and their defense contributed to O'Fallon's 28-percent shooting (14-for-50). Centralia's Jake Wood led all scorers with 24 points, including 13 in the first quarter.
Springfield SH-Griffin 52, Carlyle 44
The Class 2A state-ranked Carlyle Indians (2-1) hung tough, but eventually fell to Springfield Sacred Heart-Griffin (3-0) in the championship game of the Carlyle Kaskaskian Classic.
Cody Huels led Carlyle with 13 points and Matt Hilmes had 11 but no other Indians reached double figures. Senior David Jacob paced Griffin with 13 points and Dominic Aiello had 12.
College Prep 57, Madison 46
College Prep of Madison (4-0), a school from St. Louis, used suffocating defense and quickness to knock off Madison in the championship game of the Lebanon Thanksgiving Tournament.
Madison (3-1) fell behind 26-13, then twice cut the deficit to four points before eventually falling to defeat.
Madison's top scorer was Marquis Bourney with 16 points, while College Prep got 14 points from Kevin Baker, 11 from Terrell Herndon and 10 from Anthony Lee.
Nashville 51, Lebanon 46
Nashville outlasted Lebanon in a tight third-place game at the Lebanon Tournament by relying on a tight defensive effort that forced 14 second-half turnovers.
Scott Brown had 12 points while Chance Reuter and Keegan Anderson each contributed 10. Lebanon got 22 points from Taylor Schmitt while Zach Schoenfeld chipped in with eight points and 12 rebounds.
The teams combined for 37 fouls and shot 46 free throws.
Wesclin 55, Columbia 37
Wesclin broke open a tight game in the second quarter thanks to some hot shooting by Kyle Eversgerd, who led all scorers with 21 points.
Eversgerd had three 3-pointers during the second-quarter surge that helped the Warriors build a 31-13 halftime lead. Michael Klein added 17 points for the Warriors
Columbia got 10 points each from Michael Hunsaker and Adam Babb.
Freeburg 57, Southwestern 47
Freeburg's 6-foot-9 junior center Justin Diecker scored 17 points while Justin Livers added 11 and Griffin Diecker had 10 as the Midgets captured seventh place at the Lebanon Tournament.
Connor Robinson topped Southwestern with 14 points.