A poor game came to life when Charlie Lee headed the visitors in front on 32 minutes.
Stags wasted good chances to level before Pat Hoban’s first goal at One Call Stadium equalised on 54 minutes.
But parity was only held for three minutes as McKirdy marked his full debut by by bursting clear from his own half and showing electric pace to get into the home box and steer a low finish under Scott Shearer.
The visitors won few friends with some dramatic rolling around, timewasting and challenges.
But on the day Stags failed to find their fluency and again failed to get the rub of the green as their six game unbeaten run was unceremoniously halted.