Key statistics for predicting winners on grass courts include serve effectiveness, aces, and service games won, as these factors heavily influence performance on the fast surface. Players with strong grass-court records typically demonstrate high first-serve percentages and low double fault counts. Additionally, analyzing return game statistics like break points converted and return games won is crucial, as grass courts often favor aggressive serving. Historical performance on grass, head-to-head results, and recent form can also provide insight, while considering player movement and adaptability, as the unique bounce and speed of grass can significantly affect gameplay.