Mayo found the net three times as they won out by three points, but Roscommon’s defeat to Kerry means Monaghan are safe in division one.
Mayo won out 3-15 to 1-18 in MacHale Park as Monaghan finished with 14 men as Fintan Kelly saw red just six minutes after the restart.
Kevin McLoughlin hit the net twice in the opening half to put Mayo in the driving seat, their third goal coming after Monaghan defender Ryan Wylie deflected the ball into his own net in the 50th minute.
Mayo’s fifth victory of the campaign, and Tyrone’s win over Galway, means that James Horan’s team will meet now take on Kerry next weekend at Croke Park.
Despite playing against the gale-force wind in the opening half, Mayo led at the interval by 2-7 to 0-6.
Kevin McLoughlin’s first goal in the sixth minute set the tone and his second 25 minutes later cemented Mayo’s position as Mayo were always in control.
Half-forward clipped three superb points from play, with Jason Doherty (free), James McCormack, Aidan O’Shea and Brian Reape (mark) also on target.
Monaghan relied on the enigmatic Jack McCarron to keep them in touch. McCarron landed five points, all from play, in the first period while Monaghan’s only other scorer before the break was Conor McManus.
Flying wing-back Karl O’Connell also had a goal chance well saved by Mayo goalkeeper David Clarke in the early stages.
Monaghan’s hopes of mounting a comeback suffered an early setback when Fintan Kelly was sent off after referee Derek O’Mahony adjudged his challenge on Kevin McLoughlun to have been too robust.
Malachy O’Rourke’s men stuck to their task against the strong breeze and a goal from Darren Hughes in the 48th minute threw them a lifeline.
Mayo led 2-10 to 1-10, but they delivered an emphatic response to their visitors inside less than two minutes when Kevin McLoughlin’s palmed effort rolled into the Monaghan net after ricocheting off both Rory Beggan and Ryan Wylie.
Buoyed by their third goal, James Horan’s side tagged on points from Brendan Harrison, Jason Doherty and McLoughlin to lead by eight points at the end of the third quarter.
The game looked beyond Monaghan at that stage, but the Farneymen found the resolve to rally yet again and six unanswered points, four from Conor McManus frees.
By the 60th minute, Monaghan dragged Mayo’s lead back to two points but Mayo, steadied the ship with two scores from Diarmuid O’Connor and Donal Vaughan to seal a deserved win.
Mayo: D Clarke; S Coen, B Harrison (0-1), E O’Donoghue; P Durcan, C Barrett, J McCormack (0-1); M Ruane, A O’Shea (0-1); F Boland (0-3), J Doherty (0-2, 1f), D O’Connor (0-1); K McLoughlin (2-2), D Coen (0-1), C Diskin.
Subs: B Reape (0-1, mark) for Diskin (inj, 25); R Hennelly (0-1, 1f) for Clarke (inj, 33); J Gibbons for Ruane (47); D Drake for O’Donoghue (54); J Carr for Coen (60); D Vaughan (0-1) for McCormack; C Treacy for Boland (74).
Monaghan: R Beggan (0-1, 1f); B Kerr, D Wylie, R Wylie (1-0, OG; K O’Connell, C Boyle, K Duffy; D Hughes (1-0), N McAdam; R McAnespie (0-1), D Malone, F Kelly; C McCarthy (0-1), J McCarron (0-7, 1f), C McManus (0-8, 5fs).
Subs: S O’Hanlon for Malone; D Mone for McAdam (49); V Corey for D Wylie (55); O Duffy for McCarthy (71).
Referee: D O’Mahony (Tipperary)