Special counsel Robert Mueller could see significant changes to the way his Russia investigation operates if President Trump were to fire Deputy Attorney General Rod Rosenstein or if he were to resign, according to close observers of the Justice Department.

The question suddenly became relevant this week after it became clear that Rosenstein offered to resign following a report said he was mulling a coup against Trump. The two men are expected to meet Thursday to clear the air about the reports that Rosenstein might be dismissed, but the possibility he might still be let go has some worried that the change could prove to be significant for Mueller’s investigation.