The talented young midfielder is back in the squad for the Carling Cup clash at Coventry City after a string of fine performances for the reserves.
Named reserve team skipper, 'Jacko' has led from the front and been outstanding in central midfield of late.
The 21-year-old, who gained valuable loan experience at Swindon and Colchester last term, has won the praise of his reserve coach Colin Calderwood who pinpointed that the extra hours in pre-season had paid dividends.
Jacko agrees and explained: "I got injured towards the end of last season when I was at Colchester and I thought to myself that the only way I was going to get myself back on track was to work over the summer.
"I was lacking fitness where I was out for eight weeks and I was determined to start the season well so I did a lot of running, watched what I was eating and now it's paying off because I feel as fit as I have for a long while.
"I've also lost quite a lot of weight, about 10 pounds and that's made me more mobile and a little sharper.
"One of the wider criticisms of me was that I wasn't the quickest but there's not a lot I could do about that, but if I lost weight and was that little sharper and more mobile and get about the pitch quicker."
His all-action style in midfield added to a quality left foot has helped him stand out in that central role.
He added: "I'm happy to play anywhere really but if I could choose my best position, it would be in the middle.
"You are on the ball more and even if you are not, you can put yourself about in there.
"Obviously it's all about getting back in the first team squad. I've been working away at it for a couple of years now, not had a lot of success so far, but I'm working hard and trying to get noticed in the reserves."
John Jackson has reaped the rewards for all his hard work in the summer.