Washington figures injected themselves into the anemic struggle to avert a major league baseball strike after tonight's games. In a Rose Garden appearance, President Clinton urged players and owners to get together quickly to salvage "the most exciting baseball season in 40 years" for the fans' sake. Labor Secretary Robert Reich invited baseball fans to write him letters urging both sides to keep talking. Attorney General Janet Reno shrugged off Sen. Howard Metzenbaum's idea to strip baseball owners of a special antitrust exemption. So Metzenbaum, D-Ohio, and Sen. Orrin Hatch, R-Utah, introduced legislation "to encourage serious negotiations to prevent a strike."