Arsenal captain Thierry Henry says it will be a "massive" blow to the club if the Gunners sell defender Ashley Cole.
Henry (left) is keen for Cole to stay with Arsenal
Henry likened the potential departure of the 25-year-old - who has repeatedly been linked with a move to Chelsea - to last season's exit of Patrick Vieira.
"The loss of Vieira to Juventus was massive - like it would be if Ashley goes," Henry told The Sun newspaper.
The Gunners are also facing the loss of Spanish winger Jose Reyes, 22, who is linked with a £10m move to Real Madrid.
Cole did not travel with Arsenal for their Champions League qualifier against Dinamo Zagreb - which the Gunners won 3-0 - while Reyes was left on the bench.
That means both players are still eligible to play for another club in this season's competition, which will boost their transfer value.
If Cole joins Chelsea, we'll be trying to catch a team and giving them one of our best assets - it would be difficult to take
Chelsea boss Jose Mourinho said he was keen to sort out Cole's future within the next week, but Henry said he had reservations about selling the England international to one of Arsenal's Premiership rivals.
"Obviously we want him to stay. He is one of the best left-backs in the world. We would miss him badly," Henry said.
"We already have injuries to Gael Clichy and Philippe Senderos. We have a lot of players out.
"I don't know anything about the situation with Chelsea.
"But if he goes there it will look like we are trying to catch a team at the same time as giving them one of our best assets. It would be difficult to take."
Arsenal boss Arsene Wenger has denied that the two players' Gunners careers are over.
He admitted on Tuesday that he left Jose Reyes out of his team to face Dinamo Zagreb because the winger was "unsettled" - but insisted he was "confident" of keeping the Spaniard.
And he has said the Gunners had plans in place if Cole left.