Grandal is catching and batting seventh against Reds left-hander John Lamb, making his major league debut.
This is just the fourth start against a left-handed pitcher for Grandal this season.
The switch-hitting Grandal hasn't hit left-handers badly - he is 14-for-40 (.350) against them - but hasn't mustered any power. Of his 15 hits against southpaws, 14 are singles with one double, and he has driven in two runs against lefties.
Grandal has hit all 15 of his home runs this season against right-handed pitching, hitting .273/.384/.508 while batting from the left side.
Justin Turner, who was activated from the disabled list on Sunday, is back in the starting lineup for the first time since July 26.
Lamb, 25, was acquired from the Royals in the Johnny Cueto deal, and was 10-2 with a 2.67 ERA in 20 starts in Triple-A this season, with 117 strikeouts and 36 walks in 111⅓ innings.
Kiké Hernandez faced Lamb in four different games in Triple-A in 2014, and went 6-for-10 with a home run, a double and a walk.
Lamb also faced Joc Pederson once in 2014, and Pederson was 0-for-3 against him.
Time: 7:10 p.m. PT
TV: SportsNet LA, MLB Network