The 24-year-old Moscovite lost all three matches on his debut in the tournament last year, but struck 31 winners to overwhelm Schwartzman and go 3-0 in group play.
The world number four meets Rafael Nadal in the semi-finals on Saturday, with the Spaniard chasing a first ATP Finals crown, one of the few big titles missing from the 20-time Grand Slam champion’s CV.