They came into this season with wildly different levels of major league experience, but outfielder Randy Arozarena of the Tampa Bay Rays and second baseman Jonathan India of the Cincinnati Reds are leaving it the same way, with each being named the winner of his league’s Rookie of the Year Award on Monday.

The awards, which are given annually by the Baseball Writers’ Association of America, hardly came as a surprise: Arozarena (4.1) and India (3.9) were the top rookies in the majors in wins above replacement and each played a central role in his team’s success this year.

Arozarena, who led American League rookies in hits (145), runs (94), doubles (32), stolen bases (20) and on-base plus slugging percentage (.815) received 22 first-place votes, beating out his fellow finalists, pitcher Luis Garcia of the Houston Astros and shortstop Wander Franco of the Rays, each of whom received two. In a curiosity, Adolis García of the Texas Rangers got three first-place votes but was not a finalist because Garcia and Franco received more second-place votes.

India, who led National League rookies in runs (98), doubles (34), runs batted in (69), walks (71) and O.P.S. (.835), received 29 of 30 first-place votes. He beat out his fellow finalists, pitcher Trevor Rogers of the Miami Marlins, who received the other first-place vote, and outfielder Dylan Carlson of the St. Louis Cardinals, who received three second-place votes and 13 third-place votes.

For Arozarena, 26, the only surprising thing about the award was the fact that he was still eligible to receive it. The dynamic outfielder had played a starring role in Tampa Bay’s run to the World Series in the pandemic-shortened 2020 season, hitting .377 with 10 home runs in 20 postseason games. But that performance came after a total of only 84 regular-season at-bats over the 2019 and 2020 seasons, thus preserving his rookie eligibility.

He backed up his postseason breakout by being one of the central figures of a team that won 100 games in 2021. While the Rays were eliminated by the Boston Red Sox in a division series, Arozarena and Franco showed their value in that short series, with Arozarena executing a rare straight steal of home.

Franco, 20, was the youngest of the finalists, and had the least time in the majors, but he managed to produce 3.5 WAR in only 70 games, most of them at shortstop. He reached base in 43 consecutive games, which tied him with the Hall of Famer Frank Robinson for the longest streak in A.L. or N.L. history by a player 20 years old or younger. Garcia, whose shimmying windup for the Astros made him stand out in the postseason, was the A.L.’s best rookie starter, with a 3.48 E.R.A. and 2.6 WAR.

While India, 24, did not come into the season with Arozarena’s postseason résumé or hype, he was nearly as good, establishing himself as Cincinnati’s leadoff hitter and its most valuable position player in terms of WAR. The No. 5 pick in the 2018 draft, India rode a strong spring training to a spot on the Reds’ opening day roster. When he started at second base in the first game of the season, he became the first rookie second baseman for the Reds to do so since Pete Rose in 1963.

For the voters, that was enough to trump Carlson’s defensive versatility and 3.2 WAR and the solid pitching from Rogers, whose won-lost record of 7-8 for the Marlins obscured a terrific season in which he had a 2.64 E.R.A. and 3.5 WAR.

While rookie classes can vary, 2021 offered quite a few players with much promise besides the six finalists. Among them were batters like García of the Rangers, who hit 31 homers and had 3.8 WAR, and Patrick Wisdom of the Chicago Cubs, who hit 28 homers with an .823 O.P.S.

Top starting pitchers included Alek Manoah of the Toronto Blue Jays (9-2, 3.22 E.R.A.) and Ian Anderson of the Atlanta Braves, who had a solid regular season (9-5, 3.58 E.R.A.) and flirted with a no-hitter in the World Series.

The top rookie reliever was Garrett Whitlock of the Boston Red Sox, a Rule 5 draft pick whom Boston selected from the Yankees. He had a 1.96 E.R.A. and 81 strikeouts in 46 appearances.