Oswaldo Cabrera had a simple message to Yankees manager Aaron Boone before Game 1 of the ALDS. “Vamonos,” Cabrera said, according to Boone. Cabrera’s exclamation, which translates to “Let’s go,” came after Boone told him he would be starting at first base on Saturday night against the Kansas City Royals. The 25-year-old utilityman got the first crack at replacing Anthony Rizzo, who was left off of the ALDS roster after an 88-mph slider to the right hand last week left him with two broken fingers. “Losing Rizz is a tough blow, but Cabby has been such a steady player for us this year, and just a guy that you can count on in so many different roles,” Boone said. “He’s very prepared.” The Yankees turned to Cabrera, a switch hitter who’s better from the left side, with right-hander Michael Wacha starting for the Royals. Cabrera, whom Boone batted eighth on Saturday, hit .247 with eight home runs in 299 at-bats this season. Cabrera got the nod over lefty-swinging rookie Ben Rice, whom the Yankees called up after Rizzo’s injury, and speedy third baseman Jon Berti, who has been taking grounders at first since Rizzo went down. Cabrera appeared in 13 games — including five starts — at first base this year. He’s totaled 17 appearances at the position in his three MLB seasons and has never committed an error there. “Feel really good about him taking the field tonight for us and hopefully not only providing a spark for us offensively, but doing his thing on the defensive side, which he usually does so well,” Boone said. Rice, 25, received the bulk of the work at first base over the summer when Rizzo missed more than two months with a fractured forearm. A converted catcher, Rice was among the Yankees’ more touted prospects when he made his MLB debut on June 18. He hit seven home runs — including three on July 6 against Boston — in 152 at-bats, but he finished with a .171 average and a .613 OPS in the majors. “Any way I can contribute — if that’s starting, if that’s off the bench — I’m gonna try to do everything I can to help the team win,” Rice said Friday night, before the Yankees announced Saturday’s starter. “I’ve gotten the experience up here, a couple months, and I’ve been playing a lot more at first base throughout my time in the minors. I feel like I’m just feeling more and more prepared each time.” Berti, meanwhile, has never appeared in a regular-season game at first base but is now taking extra reps at the position, including playing there in intersquad games. Boone said Berti looks comfortable at first base and has received consideration there. “A few years ago, I played a few innings in a spring training game and kind of got a little bit of a tutorial from Don Mattingly, so a good one to get it from,” Berti, 34, told the Daily News, referring to his former manager with the Miami Marlins. “I’m familiar, but obviously it had been a few years. That’s why I kind of just brushed off the cobwebs a little bit and I feel pretty comfortable out there.” Rizzo, 35, said Friday that he was dealing with what would normally be considered a three-to-four-week injury, but that he felt encouraged by his progress after resuming hitting and throwing six days after getting plunked. The veteran has been giving pointers to his teammates about playing first base and hopes to return for the ALCS should the Yankees advance. “Whoever’s there is more than capable of manning that down, and everyone has each other’s backs,” Rizzo said. “I’m definitely confident in that.”