The 31-year-old former Wigan and Watford forward made eight appearances for the Railwaymen last season and has now been invited to join the squad for pre-season training.
"The opportunity was there for him and he has certainly worked hard on getting the weight off," Baker told the club's official website.
"He has been in to the training ground and he is looks far trimmer and fitter.
"He knew he was carrying too much weight last season and was playing catch up with his fitness but he has made that change.
"So who knows, a fit Nathan Ellington could be the answer we are looking for because we know he has quality."