Sale did secure their status in the top flight for another season at the weekend, but Diamond has revealed his disappointment with the campaign as a whole.
"In one respect, I'm embarrassed that we found ourselves in such a position," Diamond told BBC Sport.
"There's obviously some relief. It's important for the club to remain in the top flight and we've done all in our power to do that.
"We had a poor start to the season but we've got our form back since Boxing Day and it's moved us away from the bottom of the league."
Sale currently sit 10th in the table.