Marrero, who pitched for the Washington Senators from 1950-54 and was a one-time All-Star, celebrated in the same apartment he's lived in in Havana, Cuba, for about 60 years, according to a friend, Society of American Baseball Research member Kit Krieger.
"I called him up this morning," Krieger said. "My Spanish is terrible, so I did some Google translation to wish him Happy Birthday. He was very happy."
Marrero was best known as a lovable character of the game, a man who came from pre-revolution Cuba and didn't make it to the big leagues until he was 39. He won 11 games two years in a row, and he was on the American League roster for the 1951 Midsummer Classic, although he didn't pitch, having worked the day before.
He had a windmill windup and he was known to enjoy a cigar or two.
Krieger had become of a fan of Marrero based on things he had read, and organized a trip in the late 1990s to meet him. He brought various members of SABR along with him to meet the legend.
Now Krieger, who played Minor League baseball 45 years ago, visits whenever he can. Their last meeting was in January, and he sent over the best wishes and love from the other SABR members.
Since meeting Marrero, Krieger has approached some 80 former big leaguers who remembered Marrero and wrote letters that Krieger brought back to Cuba for the man to read. Some of the writers include Yogi Berra, Whitey Ford, Bob Feller, Dom DiMaggio, Gil MacDougal and George Kell.
"Everybody knew him," Krieger said. "Ted Williams had great regard for him."
Krieger said Marrero's sight is gone, but his mind is as sharp as ever. Marrero can remember intricate in-game details from more than 50 years ago with ease. He's even corrected Krieger on the score of a game.
How does he do it, even at the age of 102?
"I always ask him how he remembers these things, because it just amazes me," Krieger said.
"He says, 'When you live inside of baseball, it's easy.'"