The 26-year-old former Wolves player who has suffered a number of niggly injuries hasn’t featured at first-team level since the 4-2 defeat at Watford in August.
The wideman is in line to take on Cardiff City in Monday night’s development match in South Wales after scoring for the Under 21s in last week’s home win over Coventry City.
Boss Powell, who could also field returning frontman Joe Lolley against Cardiff, said: “It’s great to have both Adam and Joe on the way back to full fitness.
“But to my mind, they have to be 100% right, not 80%, and it’s a case of building them up in training and playing minutes on the pitch when the chance comes.
“They are both chomping at the bit to play football, but it’s crucial to be patient and ensure they are right.
“Like Joe, Adam will boost the squad and provide me with options, hopefully in the not too distant future.
“Adam has to be ready to do the job I want to be done. That is be creative, supply chances and chip in with a goal every now and then.”
Former England Under 21 international Hammill has notched 23 in a 261-game career at club level which started at Liverpool.
He has also played for Barnsley and had loan spells at Dunfermline Athletic, Southampton, Blackpool and Middlesbrough.
There have been 71 Town appearances, the first of them during a loan stint from Wolves in 2012-13, with seven goals.
His move from Molineux was made permanent during the 2013 close-season and he played as a right wing-back under Mark Robins.
Powell will tomorrow begin the countdown to Saturday’s home lunchtime derby against Sheffield Wednesday. Left-back Jack Robinson is with England Under 21s for their friendly against France in Brest on Monday.
The on-loan QPR player won his 10th cap as a substitute in Thursday’s 3-1 win over Portugal at Burnley.