Day comes with a wealth of Football League experience, having made more than 100 first team appearances for former club Mansfield, but has had to endure two injury-plagued seasons.
Speaking after Saturday's impressive 1-1 pre-season draw with QPR, Brown told the "News" he was relieved to have finally landed the tough centre back.
“Rhys will bring massive strength and athleticism to the squad,” he said.
“He is powerful in both boxes, aggressive and tough, just a real beast of a player. However, he's a big boy and big players tend to pick up injuries.
“One of the reasons I didn't play him today was because I want him to get fit. We're not in a rush to play injured players so we will be taking it gently with him.
“We did set pieces in training on Friday and he battered the life out of everybody. He likes what he has seen down here and believes the signings that we have made are very positive. He's going to be a huge asset to the club.”
With thanks to the Aldershot News.