Vlaar was recruited from Feyenoord in the summer to be the lynchpin of manager Lambert's reshaped defence, but he has been sidelined for seven weeks with a calf problem and during that period Villa have leaked a flood of goals - 22 in the last seven games.
But the Holland international is set to play in Saturday evening's Barclays Premier League derby at West Brom ahead of Tuesday's Capital One Cup semi-final second leg meeting with Bradford. And Lambert said: "There's a good chance Ron will be back. His return could be huge and would be a big lift."
He added: "He came through this week really well in training. The only thing he's lacking is match-fitness but with his muscle and the way he is, he's fine.
"He's an experienced lad and he's played a lot of big games. Ron was playing really well until he went out of the side injured almost a couple of months ago and it will be good to have him back."
He said: "We have got experienced players here.
"Gabby Agbonlahor has played loads of games. Because they're young, doesn't necessarily mean they've not played many games.
"With Darren and Richard, they are big players. Hopefully Richard's problem has been cured and Darren with his knee can get back quick. If they get back fit quick, then all the better for everyone."