To determine which player to bet on the spread in a tennis match, you should consider several factors, including the players' recent performance, head-to-head statistics, surface preferences, and physical condition. Analyze their win-loss records, especially in similar matchups, and look at how they perform on the specific surface (e.g., clay, grass, hard court) where the match will take place. Additionally, consider the players' playing styles and whether they match up well against each other. It's also essential to factor in any injuries or fatigue that might affect a player's performance. By combining these elements, you can make a more informed decision on which player to bet on.