Darby has spent most of pre-season struggling with a stomach problem but he managed to play his part in his first friendly of the summer this Saturday against Burnley at Turf Moor.
The reliable right back was only expected to possibly get the final 15-20 minutes of the contest but he started the game and managed to last nearly an hour.
Parkinson said: "He has had a really good week's training and it is a great lift for us to have him back.
"As soon as he came back out on the training pitch, the bar was raised just by his presence.
"We still have to be careful with him, we certainly didn't want to give him any longer, but I thought he was excellent.
"We will assess him over the next 48 hours or so to see how he recovers from this game but the signs are good for him so far."
Along with the sight of Darby back out on the pitch, City were also boosted by the signing of talented winger Paul Anderson just hours before the Burnley friendly.
Parkinson added: "He has played a lot of football at Championship level, and players of that ability are very hard to sign.
"I am so pleased then that we have been able to finalise the deal for Paul.
"He is at the peak of his career really and he has a lot of experience at a higher level.
"I like his hunger. He knows League 1 isn't going to be easy for him but he is ready to give us everything he's got and try to play his part in something here at the football club.
"He is a player I am sure our supporters will enjoy watching."