Vlaar held his hand up and took responsibility for Everton striker Marouane Fellaini's late equaliser in last weekend's 3-3 draw at Goodison Park.
It was the latest blow to hurt Villa from a dead-ball situation which has become their Achilles heel this season - in the Premier League and also their Capital One Cup semi-final setback against Bradford.
Vlaar knows West Ham will look to exploit their weakness in that area although the Dutch international, who has played five games in 15 days since returning from injury, can see signs of improvement.
Vlaar said: "Are teams beginning to target Villa? People will know our struggles (at set pieces). I bet they do. That's what I would have done.
"West Ham have a very strong team and play a lot of long balls. We know that so we have to be ready for that.
"It's something we have to take care of and focus on. We know the situation, I'm not afraid of that. We have to stand up and be counted, be brave enough."
Vlaar is aware of the threat that Carroll, on loan at the Hammers from Liverpool, will pose after his return from injury.
He said: "He's a very good player. I remember his goal for England in the Euros against Sweden. It was top class. That's his quality.
"We have to face that and deal with it and make sure he cannot come in that position. We also have to stop the crosses.
"He scored a lot of goals for Newcastle, it was not easy for him at Liverpool, I guess, and now he is playing at West Ham. He was injured as well for a while.
"But I think he has the ability to play at the highest level and he has quality, that is for sure. If you score goals like that (against Sweden), it says something."
Vlaar, signed from Feyenoord last summer, believes Villa are coming to terms with what is required to stem the flood of goals from corners and free-kicks.
He said: "I think we have improved on that. If you look at the last game at Everton, they had 20 corners and free-kicks all game. I think they all went well except one.
"It's too bad that it cost us the three points. That's something we work really hard on. It's getting better, but we still need to be even better.
"For everybody it was frustrating when the equaliser went in but also for me. I know my responsibility so that moment was bad."
Vlaar believes the negatives should not be allowed to outweigh the positives from the performances in the second half against Newcastle - where they were beaten 2-1 - and for long spells at Goodison Park.
He said: "You think about that moment of course (when Everton equalised) but I think there also were a lot of good moments in the game, for me but also for the team.
"I think we have to hold onto the things that went well and we played very well as a team.
"The second half against Newcastle and the 90 minutes against Everton, that's something we can build on and that's the most important thing.
"We believe in each other, that's the most important thing for now and we definitely need a result now."