When I first saw that Brian Bruney had switched his uniform number to ‘99,’ I thought that he had become the first Yankee to sport the highest of the two-digit numbers. After all, the Yankees have always been a conservative organization. They would never let one of their players wear a number like ‘99,’ or ‘0,’ or ’00.’

As so often happens, the subsequent research did not support my initial instinct. While it’s true that no Yankee has ever worn ‘0’ or ’00,” the No. 99 has come into play once before. Former Yankee outfielder Charlie Keller, a mainstay of the forties and early fifties, beat Bruney to the punch by well over 50 years. During the 1952 season—his final year in the major leagues—Keller played in only two games as part of a late-September comeback, but wore different uniform numbers each time. In one game, he wore No. 28. In the other, he took the unusual route and wore No. 99, giving himself a strange milestone achievement in Yankee lore.

I have no idea why Keller wore 99 for that one game. Perhaps he sensed the end of his career was near and wanted to do something flashy before he stepped aside completely. That’s simply speculation on my part. What is not speculation is this: Charlie Keller was one of the more underrated Yankees of his era, a damned fine hitter who registered high OPS numbers before anybody knew what in the world OPS meant.

Just how good was Charlie Keller? For his career, most of which came in pinstripes, he compiled a .410 on-base percentage and a .518 slugging percentage, both lofty numbers. Like so many left-handed power hitters in team history, he made good use of the short porch at the original Yankee Stadium, all while displaying one of the keenest batting eyes of the 1940s. As a Yankee, he never struck out as many times as he walked in a single season. Not even close. When observed more broadly, Keller was a primetime player from 1939 until 1946, a period of time that saw him reach 30-plus homeruns three times, 100 walks five times, and 100-plus RBIs three times. For nearly a decade, Keller (who played mostly in left field), center fielder Joe DiMaggio, and right fielder Tommy “Ole Reliable” Henrich formed what might have been the greatest outfield of all-time.

Keller retained his standard of excellence in World Series play, even elevating his level of power. In 72 at-bats spread over four different World Series, Keller pumped five home runs to the tune of a .611 slugging percentage. He also batted .306 in postseason play, helping the Yankees to four world championships in five attempts.

All of these accomplishments would have formed a prelude to a Hall of Fame career, if not for a chronic back injury that rendered Keller a part-time player by the age of 30 and forced him to retire completely by the age of 35. Even given his shortened career, a few Sabermetrically inclined writers have made pleas for his case as a Hall of Famer, especially if he’s given credit for having lost all of 1944 and most of 1945 to military service in World War II.

Beyond the numbers, Keller also brought some distinct imagery to the American League landscape of the forties and fifties. With his dark, bushy eyebrows and solid-as-stone 190 pounds on a five-foot, ten-inch frame, Keller took on an intimidating stature at the ballpark and in the batter’s box. As physically strong as any player of the era, Keller found himself being called “King Kong” by members of the writing establishment. Reserved and serious, Keller hated the nickname—hey, being likened to a giant gorilla has never been a desired comparison—but it fit, both in terms of description and lyrical quality. For a good part of his career, he was known as King Kong Keller first, and Charlie Keller second.

Clearly, Keller deserves to be remembered, both for his numbers and his raw power. Like Willie Randolph, Hank Bauer, Eddie Lopat, and Vic Raschi, he remains one of the most under-recognized Yankees of all-time. So the next time you see Brian Bruney wearing his No. 99 in a game, think about Charlie “King Kong” Keller, at least for a little bit.

Bruce Markusen writes “Cooperstown Confidential” for The Hardball Times.