Head coach Ashton has started the pre-tournament cull by eliminating Olly Morgan, Fraser Waters, Shane Geraghty, Louis Deacon, Andy Hazell and Magnus Lund in a revised 40-man preliminary squad.
That group could be cut further following another scheduled World Cup training camp in Bath next week.
Ashton is due to name a final 30-player squad on August 14 to defend the Webb Ellis Trophy in France during September and October.
Sale Sharks flanker Lund, who has won 10 caps, is the most surprising omission.
The 24-year-old appeared in all of England's RBS 6 Nations games last season, starting against Scotland, Italy and Ireland, but he has now fallen at the first hurdle.
And full-back Morgan, capped twice during the Six Nations before undergoing shoulder surgery, can also consider himself unlucky.
His absence though, possibly raises the prospect of Wasps starlet Danny Cipriani starting at number 15 during England's World Cup warm-up Test schedule next month.
Centre Waters, man-of-the-match when Wasps beat Leicester to be crowned 2007 European champions, Gloucester flanker Hazell and London Irish back Geraghty held slim World Cup chances, but eight times-capped Leicester lock Deacon has slipped rapidly down the pecking order.
But while World Cup hopes have been shattered for some, 2003 heroes like Lawrence Dallaglio, Mike Catt and Mark Regan remain on course to make Ashton's final squad.
"Brian has got a horrible job," said Vickery, speaking ahead of Friday's announcement.
"There is no easy way out and no easy calls.
"There are some very talented players, and everybody will have their opinions and be saying what the coach should and shouldn't do.
"The thing about the World Cup is that everyone talks about it for so long, and it seems as though it is never going to get here. Then, all of a sudden, wallop, it is here."
Ashton added: "It has been a very difficult decision to let the six players go.
"They have all worked hard in training, and it has been good working with them.
"I have taken the decision to reduce the squad now because I've had a good look at everybody in the training camp, and it is important that we spend more time giving consideration to those who will make the 22 for the first of our warm-up games against Wales on August 4, France on August 11 and the World Cup squad to be announced on August 14.
"I am considering a further cut of players at the end of next week's training, but at this stage I am not going to comment on who, or how many, as I haven't made those decisions yet."
The initial World Cup training squad of 47 announced last month included Leicester prop Julian White, but he subsequently made himself unavailable for the tournament due to family and business reasons.