Mourinho warned Chelsea's Premier League rivals of the dangers of doing late business in the transfer window, which this season closes on September 2.
"Many clubs are waiting to the last moment to make their decisions," Mourinho said. "The problem is that those decisions affect not just one or two clubs, but a lot of them.
"The one who sells has to go and buy, then they have to buy to replace, so no club is safe.
"Until the last minute somebody can go there and steal a player. I don't mean steal a player, but steal the balance that a manager has when he's working with a team.
"In that aspect, we are lucky because we don't have players to sell, so none of my players is leaving under any circumstances.
"That's good for me, but many teams will be until the last moment under pressure, without knowing how the squad is going to be."