Striker John signed on a month's loan from Crystal Palace just minutes before Thursday's loan deadline and he is expected to start.
Richard Wright could return in goal after Portsmouth recalled Asmir Begovic early from his loan spell at Portman Road.
Town were unbeaten during Begovic's six-match stay but won just once and remain in the relegation zone. Tommy Smith has missed the last three matches after injuring his hand in training but is close to a return.
Midfielders Luciano Civelli and David Norris are both making good progress in their recovery from serious knee injuries but are not due back until next month at the earliest.
The match kicks off at 3pm.