The Dodgers, though, took Cessa apart in the first inning with five straight singles that produced three runs.
Sanmartin took over in the second inning and it was lights out. He pitched five innings and gave up no runs and two hits.
Meanwhile, the Reds battled back against Walker Buehler, one of baseball’s best pitchers.
It began in the sixth with Buehler in complete command. But he walked Tyler Stephenson with two outs. Aristides Aquino, who had one hit all season and two strikeouts in his first two at bats Thursday, turned on a 2-and-2 Buehler fastball and deposited it over the left center field wall. That cut it to 3-2.
Jonathan India beat out an infield hit in the fifth and left the game with a right hamstring injury.
That meant Brandon Drury was batting in India’s spot in the seventh inning against relief pitcher David Price. And he tied the game with a two-out home run over the center field fence.
Hunter Strickland replaced Sanmartin in the seventh and got into one-out trouble, giving up a single to Chris Taylor and a walk to Cody Bellinger.
With two on and one out, left-hander Wilson arrived to douse the fire by striking out both Bellinger and pinch-hitter Gavin Lux, leaving it at 3-3.
But the Dodgers exploded for six runs in the eighth, punctuated by a three-run home run off Santillan. They sent 11 batters to the plate.
Wilson gave up a leadoff double in the eighth to Freddie Freeman. Santillan replaced Wilson and Trea Turner blooped a run-scoring single to right field, breaking the tie. Turner is on a 25-game hitting streak dating back to last season.
Justin Turner walked and Smith sank the dagger deep with his three-run home run.
And the onslaught continued against Hendrix. He gave up singles to Taylor and Bellinger, then threw a wild pitch, permitting a run. Lux walked and Betts singled for the sixth run of the inning.
That assured the Reds of their third straight defeat as they began a seven-game west coast trip to Los Angeles and San Diego.
Cessa was making his 20th major league start, but first since 2018 when he started seven games for the New York Yankees. As a starter, he was 3-11 with a 4.33 earned average, then the Yankees turned him into a relief pitcher.
He retired Betts to open the first, then gave up singles to Freeman, Trea Turner, Justin Turner, Max Muncy and Will Smith for three runs.
The Reds filled the bases with two outs in the second, an inning that began with a Joey Votto double. But Colin Moran grounded out to end the inning.
India singled to open the third but was thrown out trying to steal second. Tyler Naquin walked, but Jake Fraley flied to right and Votto grounded to second, leaving it at 3-0.