The 22-year-old played out last season and October's International Rules Series in Ireland with a damaged finger tendon in his left hand, and has done little more than run throughout the Tigers' summer program.
Riewoldt, whose breakout 2010 season won him the Coleman Medal as the competition's leading goalkicker and the Jack Dyer Medal as Richmond's best and fairest player, returned to full training just before Christmas.
"He's down to about 90 (kilos) now. He came in at 93 and probably got a little bit heavy towards the end of last year," Hardwick said.
"With the way the game's going to go this year - he played a lot of game time anyway - but we'd like to see him a bit more up the ground.
"His running today was outstanding. I think he finished in the top four or five in the 500m test, which was great."
Richmond kicked off its year at the Tan Track at Melbourne's Royal Botanical Gardens on Wednesday, with midfielder Matt White and former Bomber Bachar Houli the standout performers over distance.
Seven players posted personal-best times, with Hardwick impressed with the general condition of his group.
However, he expected it would be close to the end of the month before the five players on modified programs would rejoin their teammates.
Nathan Foley continues his recovery from the lower leg injuries that have hampered his last 18 months, while fellow midfielder Trent Cotchin will be eased back in after a strong pre-Christmas block.
"We're just going to take our time (with Foley)," Hardwick said.
"As we've said, we were never going to rush Nathan. When he's ready to go, he'll let us know.
"He's doing a lot of training and will come in fit and firing. We've just got to persevere and take some time with him."
Hardwick has been particularly pleased with the contribution of Houli, Shaun Grigg (Carlton) and Brad Miller (Melbourne), who all joined Richmond in the off-season.
He said the three players were quality characters who - in various roles - would complement the side as it built on its 15th-place finish of 2010.
