Vlaar, 30, has featured just 14 times for Villa this season due to a series of injuries, and had made just one appearance since returning from a recent knee operation which left him sidelined for four weeks.
The Dutchman missed the weekend’s 1-0 defeat at Newcastle United after a late sending off in the 2-1 home loss at Stoke, when he conceded a last-minute spot-kick, but Sherwood has revealed that his now-notorious calf problems could see Jores Okore and Ciaran Clark continue their centre-back partnership for the Baggies clash.
The Villa boss remains hopeful that his skipper will be available, but both Kieran Richardson and Aly Cissokho, who missed the Newcastle loss, are still unavailable for Tuesday night, with Matthew Lowton set to deputise in an unfamiliar left-back role for the second-consecutive game.
“Ron is back from suspension, but he's struggling with a calf [problem]. So it is going to be a late shout on Ron," said Sherwood [per TalkSport]. “You very rarely hear me crying about injuries but it's crippling at the moment.
"They are all in defensive areas of the field and it is hurting us, but you get on with it.
“Matt Lowton did very well. It’s an opportunity for the guys. They are all training very hard but I’m still trying to find my best 11.”
Villa are mired in 19th-place in the table after their seventh-straight top-fight defeat at St James’ Park, with Sherwood now having just 11 fixtures remaining to save the club from the drop.
In-form West Brom have recorded five clean sheets in their past seven games, while Villa are on course to be the Premier League’s lowest-ever scorers with 13 goals from 27 matches, but the ex-Tottenham Hotspur manager insists his team can get a positive result in the first meeting of their upcoming double-header.
“I think we will have a lot of the football,” he added. “We will need to be patient and try to open them up.
“If we score then they will need to change their plan We need to break this West Brom team down.”