In a timeline in which Trotsky is never born, or dies in childhood, or for whatever reason is not around at the time of the Russian Revolution, this would have major effects on the Russian Civil War.
Trotsky was the one who organized the Red Army from a rabble into an effective fighting force, so without someone with his organizational talents this would take longer and be less well done.
Also, he was the driving force behind the recruitment of former Tsarist officers to provide the Red Army with experienced leaders. Without him, would this be much less extensive?
It seems the abscence of Trotsky would be to the severe detriment of the Bolshevik side in the Russian Civil War? How badly would this set them back?