Floyd, 31, is returning from Tommy John surgery. The team signed him to a one-year, $4 million contract over the winter. Floyd had a 5.18 ERA and 1.61 WHIP in five starts for the White Sox last season before blowing out his elbow. He managed a 4.12 ERA and threw at least 168 innings every season from 2008-12.
Santana, also 31, bruised his thumb during an at-bat two starts ago and it forced him to leave his last start early. The team expects him to miss just one start. Santana is 3-0 with a 2.41 ERA this season. The Braves signed him to a one-year, $14 million deal in spring training after Brandon Beachy and Kris Medlen blew out their elbows and needed Tommy John surgery.
Gonzalez did not announce any rotation plans beyond Tuesday. Floyd joins Santana, Mike Minor, Alex Wood, Julio Teheran and Aaron Harang to give the team six starters for five spots. Gonzalez did say they will not use a six-man rotation. Floyd could wind up spending some time in the bullpen.
To make room on the roster for Floyd, lefty reliever Ian Thomas was sent to Triple-A. The 27-year-old had a 4.26 ERA in 6 1/3 innings this year, his MLB debut.