Lambert hoping to tie trio down
The trio will be out of contract at the end of the current season, and Lambert is keen to agree new terms with all three.
Vlaar and Delph have become among the first names of the team-sheet at Villa Park, while 19-year-old Grealish has impressed in his four appearances this season.
"We're talking to the respective parties about those so let's see what happens," said Lambert.
"You've got to put your best foot forward as such. We're talking, which is a good thing, so we'll see what can be done."
"Vlaar and Delph are different from Jack because they're seasoned pros, we'll see what happens.
"Jack is developing. He's nowhere near the finished article but this is the best place to be because he's getting a chance to be around the first team.
"He's getting little bits here and there. But he's still so far from being an established player. He's developing, which is great, and hopefully something will be done."