Pineiro, initially slated for Friday, started the series opener in Pittsburgh. Thompson, announced as Friday's starter on Thursday, will instead pitch the series finale on Sunday. Adam Wainwright remains on course to pitch on Saturday.
Manager Tony La Russa told reporters that the switch resulted from the heavy load shouldered by the Cardinals bullpen in recent days. La Russa prefers to use Pineiro, who is likely to last more innings than Thompson, in the wake of a home series that saw St. Louis relievers pitch 11 2/3 innings in three days. Thompson, meanwhile, would pitch prior to Monday's off-day.
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.