Weed, third in the SCL standings, is scheduled to finish the regular season Thursday at Fall River.
Sophomore Andrew Matheson scored the Cougars' goal on a direct kick that rolled in during a 2-1 loss to Tulelake Tuesday at Charlie Byrd Park in Weed.
Shasta Cascade League champion Tulelake remained undefeated, improving its record to 12-0-1.
Weed (8-4-1) is just behind Mount Shasta (8-1-4) in the SCL standings and just above Trinity (7-3-3) with one game left to play.
The Cougars are scheduled to conclude the regular season Thursday at Fall River (4-7-1).