Freo too good for Cats
Fremantle has overcome the Cats by 18 points in hot conditions.
Mayne's right ankle was caught under the leg of Cats' opponent Joel Hamling when tackled across the boundary line in the second half.
The 24-year-old, who was reappointed to the club's leadership group during the week, spent some time lying on the ground in agony before being helped off the field aided by trainers.
Mayne was spotted walking in the changerooms after the incident. Fremantle coach Ross Lyon admitted to Fox Footy that the incident didn't look good, but the club was positive Mayne had escaped serious injury.
It was the only sour point of an otherwise impressive start to the NAB Cup by the home side, who were led to the 7.6 (48) to 4.6 (30) victory by prolific midfielder Michael Barlow.
Barlow showed he could push to join the game's elite midfielders with 15 disposals, three clearances and two inside-50 entries in the shortened match.
Without a number of its stars heading into the fixture, including captain Matthew Pavlich, David Mundy and Nat Fyfe, the club was intent to use the early stage of the pre-season competition to expose some younger players.
And Lyon would have seen some encouraging signs, with midfielders Cameron Sutcliffe and Tom Sheridan covering the ground nicely, and Michael Walters adding some class close to goal.
After coming from behind to beat West Coast in the opening game of the night, the Cats started slowly against Freo, conceding four of the first five goals.
But a comeback in the second half, spearheaded by two goals to 22-year-old forward Mitch Brown, put them back in the contest before Fremantle kicked the final two goals to win comfortably.
After his match-winning supergoal against the Eagles, Cats captain Joel Selwood was the most impressive Cat, collecting seven disposals and booting two goals.
The loss could be costly for the Cats, with star midfielder Steve Johnson likely to come under scrutiny for contact made with Fremantle's Hayden Ballantyne.
Johnson's 'love-tap' to Ballantyne's midriff did not appear to be of serious force, but did leave the Fremantle small forward hunched over for several moments.
There is history between Ballantyne and the Cats, after a spiteful round one meeting last year, which saw Geelong defender Matthew Scarlett suspended for three weeks for striking him.
Ballantyne was also suspended for two weeks for striking Cats veteran Paul Chapman in the same match.
Fantasy snapshot: It's hard to go past Joel Selwood (MID, $530,900). Selwood grabbed 48 Dream Team points against Fremantle and only had seven disposals, showing he can score even when he doesn't have the ball. Sixteen of those points came through tackles, a big part of Selwood's make-up as an AFL Fantasy option.
FREMANTLE 0.4.2 0.7.6 (48)
GEELONG 0.2.4 0.4.6 (30)
SUPERGOALS
Fremantle: Nil
Geelong: Nil
GOALS
Fremantle: Walters 2, Crozier, Mayne, Mzungu, C.Pearce, Silvagni
Geelong: Selwood 2, Brown 2
BEST
Fremantle: Barlow, Walters, C. Pearce, D. Pearce, Sutcliffe
Geelong: Selwood, Brown, Duncan, Johnson
INJURIES
Fremantle: Mayne (ankle)
Geelong: Nil
Reports: Nil
Umpires: TBC
Official crowd: 21,804 at Patersons Stadium