The 29-year-old was left out of his national team after Wales attack coach Robert Howley revealed that the player had ruptured his finger and was dealing with a hip injury.
Despite these claims, Peel has admitted that he has been fully fit since July.
"I had a finger injury at the start of pre-season, the first week in June, but I'm fine now," BBC Sport quotes Peel as saying.
"I got cleared by the surgeon to play and to have full contact at the end of July so I'm fine, good to go."
Sale refused to allow Peel to join up with the Welsh squad in July due to the English Premiership ruling stating that clubs do not have to release players until August 4.