Hardwick said that although Yarran did not come to Richmond in peak fitness, there were reasons behind that.
"He probably didn't come in with the best conditioning. Chris knows that. He's responsible for that," he said.
"The thing that we didn't probably realise was that he's been having some plantar fasciitis … over a little bit of time. We didn't realise the serious nature of it until we went and had a pretty significant scan.
"His training capacity has been reduced because of it, so he hasn't been able to train at AFL intensity."
Yarran had foot surgery to fix the issue and is not expected to play for another five weeks.
The Blues traded Yarran, 25, at the end of last season to Richmond for draft pick No. 19.
He struggled with a calf injury throughout the pre-season and didn't play in the NAB Challenge. The extent of his football in Richmond colours was 45 minutes in a VFL intraclub match.
http://www.afl.com.au/news/2016-03-26/tigers-injury-woes-grow-midfielder-shane-edwards-fractures-hand