The ever-present skipper is set to miss the Colchester clash with a virus and Hanson is still struggling with the groin strain which forced him out of the Brentford defeat.
But Andrew Davies, another absentee at Griffin Park, trained fine yesterday and should be fit.
Matty Dolan is pushing to replace Jones after being left out of the weekend squad because City had the maximum five loans.
Parkinson said: “Gary had the virus last week but came in Thursday and said he felt great. I just think the heat from the weekend and the demanding game it was has set him back a bit.
“He’s been immense this season and it’s typical of Gaz that he kept going on Saturday. Maybe he should have said at half-time that he was feeling poorly.
“But we’ve got players chomping at the bit. If you go back to this stage last year, we changed the squad round all the time and we’re going to have to do that again.”
Hanson travelled with the team yesterday and will be assessed late on. Andy Gray could be called in if he doesn’t make it.
Colchester sit two points behind City and with Peter Taylor’s Gillingham due at Valley Parade next, Parkinson’s men need positive results to prevent them being sucked in to the relegation scrap.
Parkinson added: “This is a big week for us. It’s important that we’ve put in two really strong performances by Saturday evening.
“I know it sounds very simplistic but, as we said before the Port Vale game recently, let’s make sure the 11 go out there and play well for 90 minutes.
“I’m not saying we didn’t do that at Brentford but we had a few players out and came up against a very good team.
“You look back at that period against Port Vale and MK Dons and the second half against Crewe. We need to replicate that kind of performance on our travels.”
Colchester beat Coventry 2-1 on Saturday – their first win for seven games – but the pitch is expected to be very poor.
Parkinson cut his managerial teeth with the U’s and steered them into the second tier in 2006 before leaving for Hull. He is expecting a decent reception from the locals.
He said: “When I first left, the supporters weren’t very pleased that I’d gone when I did, after just getting promotion. But I had my reasons, which I still stand by.
“But over the time people have realised the job I did there and whenever I bump into any Colchester fans on my travels up and down the country, I always have a good chat with them.
“It was my first managerial job and a fantastic learning curve. It was a club with very little resources but everyone was great with me.
“My kids all went to school there, so my family have got an affinity with that area.
“I went down last Tuesday and saw some familiar faces. Layer Road had its own unique atmosphere and it’s a different type of club now but I’m looking forward to going back.”
Parkinson will also be looking for a first win at the Weston Homes Community Stadium – his previous visits as Charlton boss saw a 3-0 defeat and 3-3 draw with two sent off.
“We had a terrific start to the season and had won all six games,” he recalled. “We went to Colchester and passed them off the pitch for 25 minutes.
“But we didn’t score and ended up getting beaten. Then we went there again for an end-to-end game that could have gone either way.
“They are always entertaining and I think this game will be similar. Colchester are quite an open, expansive team and I think there will be chances at both ends.”