"It just seemed to me that some batters hit certain pitchers better than others, and maybe it would be helpful to know those numbers," Weaver said recently.
The year was 1968, at the close of Weaver's first season managing the Orioles. The analysis and use of statistical data was still taboo in major league dugouts.
Undeterred, Weaver asked Bob Brown, the Orioles' publicity director, if it was possible to ascertain how Orioles hitters fared individually against opposing pitchers, and also how Orioles pitchers fared against opposing hitters.
No problem, Brown said.
"It sounds like a lot of work, but it was actually pretty easy to break out," Brown recalled.
Beginning with the 1969 season, Weaver used such statistics when making decisions before and during games. Although the Orioles won three American League pennants and a World Series title over the next three seasons, other managers would not follow his lead for another decade.
"It was a lot of help in a lot of ways," said Weaver, 74, who ultimately managed six Orioles teams into the postseason and was inducted into the baseball Hall of Fame in 1996. He now resides in South Florida.
Weaver relied on the numbers primarily when making out lineups and choosing pinch hitters.
"He always had the right answers for not playing you or doing whatever he wanted," said Orioles coach Elrod Hendricks, who played in the major leagues from 1968-79, mostly under Weaver.
Much of what the stats revealed wasn't surprising. Left-handed hitters such as Boog Powell tended to struggle against left-handed pitchers such as Jim Kaat and Mickey Lolich. Certain right-handed hitters struggled against certain right-handed pitchers, such as Rick Dempsey against Ferguson Jenkins.
Occasionally, there was a stunner such as light-hitting shortstop Mark Belanger's success against Nolan Ryan.
Brown continually updated the individualized statistics on sheets of paper - not index cards, as legend has it.
"I did it for years and years and nary an index card was used," said Brown, now 72 and also living in South Florida. "I'm not sure where that [index card] rumor started. But it started and never stopped."
The confusion possibly arose because Weaver also kept index cards containing information on opposing hitters' tendencies, which he and his pitching coaches used to help prepare their pitchers. Some statistical data was on those cards.
But it was Brown's sheets of paper, showing Orioles hitters' batting averages against opposing pitchers, that spawned the legend.
Brown, who worked for the Orioles for 35 years, maintained a separate sheet for every opposing pitcher and updated each after every series, using white-out and a pencil. He did the math either by hand or with the help of a booklet titled "Batting Averages at a Glance," published by The Sporting News.
"No calculators, no computers," Brown said.
Before every series, Brown gathered the sheets for each of the opponents' pitchers and gave them to Weaver. Afterward, Brown updated them before moving on to the Orioles' next opponent.
"We kept career numbers, so in the beginning, when we didn't have data stretching back very far, the numbers weren't quite as telling," Brown said. "But we worked with some other teams and succeeded in getting data going back.
"Basically, as time went on, the numbers covered a greater period of time and became more revealing and quite useful."
Brown began shifting the chore in the late 1970s to Charles Steinberg, a Gilman School graduate who joined the Orioles as an intern and is now the Boston Red Sox's executive vice president of public affairs.
Weaver, who retired after the 1982 season (and came back in 1985 and 1986), said he believes Tony La Russa was the next manager after him to use such statistics. La Russa, who now manages the St. Louis Cardinals, broke into the major leagues as a manager in 1979.
Before Weaver and La Russa, individualized statistics were seldom used in the majors. Hall of Fame manager John McGraw platooned players in the early 1900s, suggesting he had ideas about probability. Branch Rickey employed a stat guy while running the Brooklyn Dodgers in the 1940s. The Houston Astros and Chicago Cubs tinkered with information derived by computers in the 1960s.
Most managers who dared use any objective criteria in the dugout were ridiculed. Hunches were deemed more important.
Hendricks recalled former Orioles second baseman Davey Johnson bringing a computer printout to the park and showing it to then-manager Hank Bauer in 1968.
"Davey had studied the numbers and had it all figured out where he should be batting fifth," Hendricks said. "Hank told him to take that computer and stick it."
Not until 1981, after Weaver and La Russa had experienced success, did the STATS statistical service began operating with the goal of providing teams with individualized numbers.
"The numbers gave Earl an excuse to do what he wanted," Brown said. "Guys couldn't complain when he gave them a day off because the numbers backed up what he was doing."
Weaver laughed at the idea that players weren't happy taking days off.
"I didn't have a lot of right-handed hitters complaining when I gave them the day off against Ryan," he said.
Hendricks said some players were initially skeptical about the use of statistics but quickly became converts.
"It just made sense," said Hendricks, who batted .222 in his Orioles career as part of a catching platoon with a succession of others.
Weaver's reliance on statistics was never more important than during Game 1 of the 1979 American League Championship Series between the Orioles and California Angels at Memorial Stadium. John Montague was pitching for Angels in the bottom of the 10th inning. Weaver went to check his sheet on Montague before selecting a pinch hitter.
There was no Montague sheet.
"He had been traded from the Seattle Mariners to the Angels late in the season, and we still had him filed with the Mariners," Brown said. "The other team files were in my office."
When Weaver discovered the omission, he asked pitching coach Ray Miller to phone Brown in the press box. Brown then phoned an intern manning the team's offices during the game. The intern located the Montague sheet and ran it out to the dugout.
"He gave it to [Miller] in the tunnel, and Ray ran it up to Earl," Brown said.
The numbers indicated John Lowenstein had succeeded against Montague and would be a dangerous pinch hitter. Weaver sent Lowenstein to the plate, and Lowenstein hit a three-run homer to win the game. The Orioles went on to win the series in four games.
"Earl never ceased to amaze me," Lowenstein recalled. "Montague was pitching differently than he had for Seattle, throwing more forkballs, so the previous numbers really didn't mean much. But Earl was very proud of his little system."
Hendricks recalled a game at Yankee Stadium in 1969 when Weaver let him bat with the bases loaded against a pitcher Hendricks had never hit.
"He told me I was 0-for-12 lifetime as I was heading to the plate; I couldn't believe he let me bat," Hendricks said. "I hit a double off the wall."
Few of Weaver's sheets and cards can be found today. Neither Brown nor Weaver has any. A few loose-leaf notebooks are in the Orioles' archives.
One of the notebooks provides the Orioles hitters' career averages against the Milwaukee Brewers' pitchers over a period of years through 1980. The name of a pitcher is at the top of each page, with the hitters' results against that pitcher below.
For instance, the Orioles' Ken Singleton was hitting .360 in his career against the Brewers' Moose Haas through 1980, while the Orioles' Doug DeCinces was hitting just .217 against Haas.
Weaver could have looked at that page and opted to give DeCinces, his third baseman, a day off against Haas.
By the mid-'80s, most managers had access to that data as well as numbers even more sophisticated. Such information is, of course, commonly used today.
"It's hard to believe, given the dependence on such information today, that we went without it so recently," Brown said. "It all started with Earl."