Branch Rickey is most famous for helping break Major League Baseball's color barrier by signing Jackie Robinson to a minor league contract while he was general manager of the Brooklyn Dodgers in 1945, but he was also partly responsible for bringing fellow future Hall of Famer Roberto Clemente to Pittsburgh.

Rickey was working as the general manager for the Pirates, who were coming off their third consecutive 100-loss season, in 1954, when Pittsburgh used the first pick in the annual rookie draft to select Clemente. (The Dodgers had signed Clemente earlier in the year, but he was left unprotected in the draft because Brooklyn hadn't kept him on its major league roster all season.) Rickey wasn't overly impressed with Clemente the first time he saw him play after the draft and recommended the outfielder spend the 1955 season in the minor leagues.

"I have been told very often from many sources about his running speed. I was sorely disappointed in it," Rickey wrote in January 1955 after watching Clemente play a winter league game in Puerto Rico. "His running form is bad, definitely bad, and based upon what I saw tonight, he has only a bit above average major league running speed. He has a beautiful throwing arm. He throws the ball down and it really goes places. . . . His form at the plate is perfect."

Clemente played 124 games with the Pirates in 1955, the first of his remarkable 18-season career. The scouting report on Clemente is one of about 1,750 written by Rickey in the 1950s and 1960s that were recently digitized by the Library of Congress. The collection, which is not yet fully searchable, reveals how blunt Rickey often was in his assessment of minor leaguers in the 1950s.

On Pedro Ballester: "He is no good in any way and should have his unconditional release."

On Ron Bell: "Can't throw a lick and I don't believe he can hit a lick. He must be able to run or he wouldn't be here. Good average runner."

On Tom Biscotti: "Not worth anything."

Rickey, who helped develop baseball's farm system while serving as the St. Louis Cardinals' general manager during the 1920s and 1930s, saw potential in pitcher Ronald Blackburn, who appeared in 64 games, mostly as a reliever, for the Pirates in 1958 and 1959.

"I like him," Rickey wrote. "I think he has a chance to go places."

Rickey was right about Pirates second baseman Bill Mazeroski, the hero of the 1960 World Series, writing during spring training in 1956 that Mazeroski "could be a quicky . . . and take our second base job before the year is over." He was also high on a young Orioles second baseman named Dave Johnson, and suggested that Pittsburgh try to trade for the infielder.

"Tall, slim right-hander now playing second base," Rickey wrote of the future Orioles and Nationals manager. "21 years old. First year player. Good looking fielder. Good batting form. A major league possibility. Try to include him in any possible deal with Baltimore."

Baltimore held on to Johnson and he helped the Orioles win a pair of World Series titles.

Other highlights in the collection include Rickey's scouting reports of Hank Aaron ("surely one of the greatest hitters in baseball today"); Don Drysdale ("a lot of artistry about this boy"); and Dave DeBusschere ("should become a corking good major league pitcher"). DeBusschere, who pitched two seasons for the White Sox, eventually gave up baseball and found more success during his NBA career with the Knicks and Pistons.

The Library of Congress says the digitization of Rickey's papers is part of a larger effort to make historical materials available online, and is a preview of the upcoming "Baseball Americana" exhibit that will open June 29. Featured artifacts of the exhibit will include "the first handwritten and printed references to baseball in America; early rules of the game; historical baseball images, including a lithograph of prisoners of war playing baseball in captivity during the Civil War and photographs from baseball throughout the decades; familiar players from some of the great collections of early baseball cards; beloved baseball movies and early flickering footage from the late 1800s; broadcasts of iconic baseball moments and rare interviews and clips of Hall of Fame players, including Babe Ruth, Jackie Robinson and others."

"I have loved baseball my whole life," Librarian of Congress Carla Hayden said in a release. "In fact, when I was little I wanted to be a shortstop. I am really excited to connect fans of the game with this extraordinary history. The Library's Branch Rickey Collection reveals on how he discovered some of baseball's greatest players. His spot-on assessment of players will take fans and historians into the mind of a sports genius."