The League Two side were due to bring an XI to Privett Park to face a mixture of Boro' s under-23 and under-18 squad players last night.
However, Gosport boss Gale revealed the club notice of Forest Green's decision not to bring a team down to the south coast at 12.30pm.
It was a further pre-season blow for Boro, who saw Pompey call off a scheduled friendly meeting while they launched an 'immediate investigation' into alleged racists messages sent in an academy team social media group - the Blues have since sacked three youth players.
Gale told how he was informed the Forest Green game was pulled because of an ongoing 'internal matter' at the League Two outfit.
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The Boro boss said: ‘It’s an internal matter at Forest Green, but I’m disappointed to say the least.
‘It wasn’t made by Jimmy Ball (the decision), who is obviously the academy manager there, it was made by someone else at the football club.
‘At such late notice, it’s obviously very disappointing. Some of these league clubs - be it they were only going to bring some young lads and a few professionals - it’s irrelevant.
‘It’s a Football League club and it messed up our preparations to a degree. We ended up having an in-house game but it wasn’t the same magnitude.
‘People wanted to come and watch the game, it’s a disappointment, but it is what it is.
‘We can’t control what goes on in other football clubs, unfortunately, it was a decision made by someone else at the football club.
‘We were told at 12.30pm yesterday, which is not ideal, I don’t blame Jimmy at all - it’s not Jimmy’s fault. He’s worked hard to get me the game, but it was a big disappointment.’
Instead of welcoming Football League Forest Green, Gosport played host to an in-house match involving under-23s and under-18s players.
But Gale is now looking forward now rather than reflecting on the Forest Green call off.
Boro make the trip to National League South side Hungerford on Saturday in their final pre-season friendly before the big Southern League Premier South kick-off.
By that time, Gale is hopeful of having secured deals to bring in former Pompey prospect Harvey Rew and Aldershot Town goalkeeper Ryan Hall on a season-long loan, who both featured in Saturday’s friendly defeat at Hawks.