Launceston has heaped more misery on struggling Clarence, bolting to a 13.14 (82) to 4.2 (26) win at home.
On a day when Dylan Riley made a successful return to the TSL, the Blues asserted their authority with a five-goal second quarter before holding the Roos to just eight points in the second half.
The win put an eight-point buffer and healthy percentage between the Blues and fifth-placed Kingborough, with the two sides set to meet at Kingston next weekend.
"It was a really strong performance," Blues coach Mitch Thorp said.
"Everyone was hurting a bit after the North Launny loss and everyone was keen to come out and make amends and lock up a finals spot, which we've probably done today, which is really important and really pleasing."
Midfield bull Jobi Harper saved one of his best performances of the season for the worst weather conditions seen at Windsor Park this year, racking up 32 touches and a goal to be best on ground, while Alec Wright was solid down back in Simon Vandervelde's absence.
Thorp kicked the Blues' first two goals en route to four for the game.
"It was really tough conditions - wet and muddy - and we were pretty powerful around the ball which is a credit to the midfield," he said.
"They got to work pretty early in the game and we put a nice gap in the margin which made the second half a bit easier when the rain came.
"It's an attitude and mindset when you roll up to a game and it's pouring down with rain and mud everywhere - I thought our midfielders really got their hands dirty.
"We were able to lock the ball in out forward half and get some repeat entries so credit to our midfielders."
Riley kicked three first-half goals in a promising return display and looked to have slotted seamlessly back into the Blues' 22 after half a season at Meander Valley.
"Dylan played pretty close to goal today and certainly gave us an option every time we went forward," Thorp said.
"He hasn't missed a beat, he's a very talented player and the boys are rapt to have him back in."
- Launceston 3.1, 8.2, 10.4, 13.4 (82)
- Clarence 1.0, 3.0, 3.0, 4.2 (26)
- GOALS, Launceston : M. Thorp 4, D. Riley 3, J. Blackberry 2, J. Harper 1, J. Hinds 1, A. Wright 1, B. Killalea
- Clarence : J. Harper 1, J. Webberley 1, T. Hope 1, K. Howlett 1
- BEST, Launceston : J. Harper, M. Thorp, D. Riley, A. Wright, R. Tyrrell, F. Seymour
- Clarence : O. Davis, B. Jones, J. Holmes, C. Riley, J. Webberley, K. Howlett