A late-season clash, that only came to life in the closing stages, went Macc's way, despite their hosts' dominance.
A rugged defensive effort saw the Silkmen extend their unbeaten run to four games in a contest that offered precious little for the football purist.
Macc survived concerted pressure from Barnet in the first half, with Daniel Leach's rising header and a shot from Micah Hyde the closest they came to breaking the deadlock.
Macc had failed to must any attempts on goal in the first period but 10 minutes after the restart Sinclair latched onto John Rooney's neat pass and blasted inside Jake Cole's near post. The keeper had been a virtual spectator for the first 45 minutes and had precious little to do after Sinclair's strike.
Cole did have a hand in Macc's winner however, as his scuffed clearance fell perfectly for Macc's Lee Bell, who slotted home the second a minute from time.
There was time for Barnet substitute Ed Upson to fire in a consolation but Macc held out during four minutes of injury time to clock up their third win in four.
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