Delph has received plenty of praise for his performances during the current campaign and Weimann believes that his teammate is still improving in a Villa shirt.
"Fabian has been brilliant," the Austrian forward told the club's official website. "It's as simple as that.
"He's been our best player all season. He's just been inspirational on the pitch and he's a top lad to have in the dressing room too.
"He's improving all the time. He's getting better and better with each passing week."
Delph scored the winner as Villa produced an upset to beat Chelsea last Saturday.