Brown was 8-for-10 from the field, including 3-for-3 from 3-point range. He also had four rebounds, three assists and three steals.
Doolin was 7-for-16, and he and Mark Dunn each had seven of the Pioneers' 33 rebounds.
"This was one of Doolin's better games overall, and Brown shot the ball well, but it was a total team effort in which everyone contributed," Tatum said.
Harrodsburg had 14 assists, 11 steals and only eight turnovers.
HARRODSBURG (8-11) - Robbie Merriman 3, Shane Webb 10, Mariqus Brown 21, Mark Dunn 10, Travis White 2, Adam Gray 2, Justin Doolin 18.
SAYRE (6-10) - Dee Smith 7, Will Campbell 5, Doug Arnold 6, Bush Guess 16, Ben Guess 2, Will Bowman 6, Spears Hinkle 4, Colin O'Rourke 2.
Marion County 58, Mercer County 56 - At Harrodsburg, two free throws with 0.9 seconds left made the difference as Marion (13-6) fought off host Mercer (7-11).
Mercer trailed by as many as 21 points in the first half and 18 at halftime, but the Scotties outscored Marion 37-21 in the second half.
"We did not play well in the first half but in the second half we used man-to-man defense to get back in the game," Mercer assistant coach Chad Mayes said.
The game was tied at 56-all and Marion was holding for a final shot. The shot missed the mark, but one of the Knights rebounded and drew a foul that led to the winning free throws.
Jordan Lyons led Mercer with 23 points, followed by Clif Watkins with 13 and Kameron McRay with 12.
Marrian Yocum had a game-high 24 points for Marion.
MARION (13-6) - Harris 7, Campbell 2, Thomas 16, Buckman 4, Yocum 24, Smalley 5.
MERCER (7-11) - Clif Watkins 13, Kameron McRay 12, Jordan Lyons 23, John Lyons 3, Michael Bottoms 5.