Like Barry Bonds in the 2000s edition of this series, there was no debate over who the player would be. Instead, the only question was which year, and even that wasn't a difficult choice.
1956 Mickey Mantle (12.9 bWAR)
Mantle was already a household name and a top player by '56, the year his production finally satisfied the lofty expectations that had burdened him since his rookie season five years earlier. His career had been following a smooth upward trajectory, bearing an eery resemblance to Ken Griffey Jr.'s early seasons. Even though he put up big numbers in '55, there was a gnawing suspicion that Yankee fans still hadn't seen the best of this kid, the one who was supposed to be on par with Babe Ruth, Lou Gehrig, and his predecessor in center, Joe DiMaggio. Although he was only 24 years old, he was a very accomplished player; he had already played in four World Series (three of them against Snider's Dodgers), winning three of them, had made four straight All-Star squads, and earned a pair of top-five MVP finishes (getting robbed the previous year, when voters inexplicbly preferred teammate Yogi Berra over Mantle's 9.5 bWAR).
At the time he was locked in a three-way battle with Willie Mays and Duke Snider for the title of best centerfielder in the city, but in '56 he was able to separate himself from the pack. After doubling his salary from the year before, Muscles sprinted out of the gate by blasting a pair of home runs on Opening Day, putting up enormous numbers in May and holding his average above .400 into early June. He was keeping up with Ruth's record-setting home run pace for much of the season, entering September with 47 home runs. Unfortunately Mickey slumped down the stretch; the season's final month was his worst by far and he managed to clear the fences just five more times. Five years later he would challenge the Babe once again, teaming up with Roger Maris in a mesmerizing home run chase that wouldn't be replicated until the Mark McGwire/Sammy Sosa race at the end of the century. The Mick would finish with 54 four-baggers (a career high) after a hip infection knocked him out of the race late in the season, leaving Maris to ultimately rewrite the record books.
Mantle won the major league triple crown after his "favorite summer," leading the Show with 52 home runs, 130 RBI and a .353 batting average (nobody in the Junior Circuit came within 20 of his home run total, but he didn't shake Ted Williams in batting average until the final week of the season and Al Kaline finished with just two fewer RBI). His 132 runs, .705 slugging percentage, 1.169 OPS, 210 OPS+ and 376 total bases also ranked first among all big leaguers. The Commerce Comet set career highs in almost every category and helped lead the Bombers to 97 wins and another World Series flag. He slugged three home runs against their crosstown rivals, the Brooklyn Dodgers, in a rematch of the previous year's Fall Classic (when the Boys of Summer finally got the best of their American League nemesis). In the offseason he captured his first MVP award, and did so unanimously by receiving all 24 first place votes. He also received the Hickok Belt as the top professional athlete of the year, was recognized as Associated Press Male Athlete of the Year and was named ML Player of the Year by Sporting News. On the strength of this monster year, Mantle nearly doubled his salary for the 1957 season.
Some more stats from Mantle's banner year:
-Also led the American League in bWAR, extra base hits, runs created, adjusted batting runs, adjusted batting wins, times on base, and offensive win percentage
-The switch hitter batted .342/.459/.737 from the left side, .375/.474/.642 from his natural right side
-He didn't ground into any double plays in May and June, and bounced into just four all year long (one in each month except for May and June), a match of his 1955 total. He did not hit into any twin-killings at home that season.
-Batted an otherworldly .444/.582/.861 with runners in scoring position. With runners in scoring position and two outs, his batting average was an even .500. It was no surprise, then, that all six of his intentional walks came with men in scoring position
-His BABiP (.353) matched his batting average
-Stole ten bases, marking the first time in his career he cracked double digits. He was caught stealing just one time, and went on to swipe at least a dozen bases in each of the following five seasons
-Inflicted the majority of his damage in May and August, when he socked a combined 29 home runs and piled up 88 of his 188 hits.