As the U.S. portion of the major league schedule got under way Sunday night, President Bush said he thought December’s Mitchell Report on drugs in baseball ‘‘was part of the cleansing process.’’

‘‘I’m happy with the recognition that it was a problem,’’ Bush said Sunday night during the ESPN broadcast after throwing the ceremonial first pitch at Nationals Park. ‘‘I certainly hope the players continue to work to clean up the sport.’’

A day ahead of most other teams, the Washington Nationals beat the Atlanta Braves 3-2 on Ryan Zimmerman’s ninth-inning homer off Peter Moylan. They opened their new ballpark with a little help from the former Texas Rangers owner, who expressed worry that performance-enhancing drugs will be developed that escape detection.