Defender Ben Stirling hobbled off nine minutes before the half-time interval following a robust tackle as the Citizens succumbed to a 5-0 defeat to Stirling Albion in their final League Two fixture of the season.
Maybury, who replaced Gary Naysmith in March, made a raft of changes with one eye on the Sons' visit to Ainslie Park.
And the former Hearts and Hibs full-back revealed the on-loan Hamilton player is almost certainly out of Tuesday night's tie.
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"We spoke about it as staff what was the best way to approach the game at Stirling because it didn't really matter to us," Maybury said. "If we'd needed to win the game then we would have gone about it differently. But it was a last opportunity to make sure everyone is up to speed. There have been one or two who haven't played much since I arrived at the club or others who are coming back from injury.
“But the negative is that Ben Stirling looks to have taken a sore one and he's probably out. We just wanted to make sure that come Tuesday night and Saturday we have everyone available who is fit. We're going to need everyone over the course of the play-offs as we aim to get into the second week."
Former hearts man Dale Carrick netted a first-half hat-trick with Kyle Banner and Jack Leitch also on target for the Binos at Forthbank.
Maybury added: "I take the responsibility for Saturday's defeat. We were just a bit disjointed as we were asking boys to play a slightly different position and we didn't quite get to grips with it. But at the end of the day, whether we'd won, drawn or lost the game it didn't really matter. Yes, I would have liked a different scoreline, but it makes no difference whatsoever as my total focus is on this week.
"I watched Dumbarton maybe two or three times before I even came to the club so I am aware what their strengths are. I'm a lot more aware of what my team can do now and the options available. Come Tuesday we'll be ready."