The Villa squad was hit hard by a virus last weekend when they lost 3-0 at home to Arsenal, their first league defeat of the season.

"We closed the training ground down on Monday and some of the lads still came back feeling a bit groggy on Tuesday," said Lambert at his press conference on Thursday.

"Today they feel a lot better so hopefully it's out of their system. Everybody's trained and hopefully we'll get a clean bill of health for Saturday.

"We don't know where it came from. Lads were just going down all the time. I've never known it where lads are throwing up on the morning of a game.

"Ashley Westwood was sick in the warm-up, Nathan Baker, Darren Bent and Andi Weimann were at half-time. We were really struggling. It's not an excuse but it's a fact. We could have been better defensively but we weren't at 100 per cent."

Belgian striker Christan Benteke has returned to training following his lengthy lay-off with an Achilles injury, but the Stamford Bridge game will come just too soon for him.

The 23-year-old could, however, be available for the match against champions Manchester City at Villa Park on October 4.

Lambert added: "He's getting closer. Next week we will see how he is for the Man City game.

"I'm not saying he'll start, or anything, but he's certainly getting close."