The 22-year-old former Darlington man missed most of the tail end of last season with a groin injury, but started at left-back on Monday night as Town beat Hitchin 1-0 at Top Field.
Buckle said: “I must say that Greg had a tough end to the season and really tried to get back.
“I’ve been looking forward to watching him and he’s worked his socks off in training as have all the lads, but he’s really pushed himself.
“I think he’s realised the levels of fitness have gone up and last year he was struggling a little bit.
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“But now he’s up-and-running, he’s worked hard, started in that left-back position and done well.”
The boss believes the competition for places is good for all of his players, adding: “He knows he’s got (Lathaniel) Rowe-Turner breathing down his neck and that pushes players on. It’s something you need in a squad and as a player.
“I also thought Rowe-Turner did excellent as a left-sided centre-half. You can see that he can do either and he’s got electric pace which always comes in handy.”
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