Flores has not played in the majors since 2012 with the Nationals. He spent the 2014 season with the Royals' Triple-A affiliate at Omaha, batting .248 with five home runs and 21 RBI in 40 games.
Wall wasn't 100 percent certain he would play in Saturday's game because of a lingering ankle injury as well as persistent migraines. He is visiting a doctor about the migraines later on Friday. Wall said he should have sat out Wednesday's game as well.
Pierce is dealing with a toe injury that caused him to miss Tuesday's game, even though he did play Wednesday.