Indians closer Cody Allen (2-4) allowed six runs after getting two outs in the ninth, the last three charged on Votto's extra-base hit off Otero.
And it was all thanks to a miscommunication between Francona and Indians pitching coach Carl Willis.
Francona's affinity for nicknames - Perez is "OP;" Otero is "OT" - cost him dearly, too.
"When I saw OT coming through the gate, it was not the guy I was expecting", Francona told reporters, per ESPN.
Jul 10, 2018; Cleveland, OH, USA; Cleveland Indians manager Terry Francona (77) and the Indians infield point to the dugout during a pitching change during the ninth inning against the Cincinnati Reds at Progressive Field.
"That one lands squarely on me".
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Bauer got the start for Cleveland and shut Cincinnati out on three hits, striking out 12 over eight innings.
Willis, who rejoined the staff this season, accepted responsibility for the mistake.
Said Willis: "I made the mistake. Not that [Otero] can't get the job done; just wasn't the right matchup". "I've got to be responsible for that". Eugenio Suarez added an RBI single two batters later.
As Francona explained after the game, the mishap occurred when he called the bullpen to start warming up the next reliever.
Former Cleveland reliever Kyle Crockett (1-0) netted the final two outs in the eighth after righty Sal Romano went the first 7 1/3 innings. But Votto was actually 0-for-4 vs Otero until the double that won the game.
Regardless of where the blame was placed, the end result was a stirring comeback win for the Reds and a night to forget for the Indians.