The versatile Irish international was given the task of providing our spearhead when he replaced Robbie Keane after 36 minutes against Newcastle last Wednesday and then entered the fray at the other end of the pitch against Chelsea when Anthony Gardner suffered a hamstring injury in the first half at Stamford Bridge.
He was back on striking duty for the reserves on Monday, playing the full 90 minutes against Nottingham Forest at Stevenage.
"It's been hard work, to be honest," admitted Gary. "I played an hour up front against Newcastle, an hour at the back at Chelsea, then 90 minutes here so it has been hard.
"Hopefully I will profit from it though and in the coming weeks my fitness will get a bit better."
Both Premiership matches provided a big test of character for the 23-year-old, entering play as an injury replacement in games of such magnitude and tension is no easy proposition.
"Everyone know that it is the hardest thing in football coming on as sub - unless it is the last ten minutes. It is hard to get in tune with the game straight away.
"I was a bit disappointed after the Newcastle game, but I think I did alright against Chelsea. It was a good point for us and hopefully I've put my name in the hat for the game against Sunderland on Saturday."
Gary Doherty has gone from front to back and up front again in the last six days.