Ibrahimovic has been absent since April after suffering a serious knee injury, but United still opted to hand the 36-year-old a new contract after scoring 28 goals last season.
The 54-year-old told reporters: "Zlatan is here, under our control, working as I would expect, so, so hard, but he's not back in a week or a couple of weeks.
"Let's let him take his time and be back in the right moment. Do I think he will be back in 2017? Yes I do, but it's just a feeling."
Ibrahimovic was named in United's squad for the Champions League group stages, but the veteran striker may have to wait until the last 16 in February.