Knuckles' inclusion in Sega Superstars Tennis would significantly alter the gameplay dynamics, introducing a unique blend of power and defensive capabilities. His playstyle would likely center around a powerful, albeit slower, approach.

Serve: Knuckles' serve would be a high-risk, high-reward proposition. Imagine a powerful, slow-moving serve with significant topspin, difficult to return cleanly but vulnerable to well-timed drop shots or aggressive returns. A successful serve could set up devastating follow-up shots. A missed serve, however, could leave him vulnerable.

Groundstrokes: His groundstrokes would be characterized by raw power, capable of generating considerable speed and depth. However, this power would come at the cost of precision and control. Expect powerful, potentially unpredictable shots that could easily go long or wide if not perfectly executed. His forehand could be a particularly devastating weapon, capable of overpowering opponents.

Volleys: Knuckles' volleys would be a mix of power and defensive positioning. He wouldn't be as nimble as some of the faster characters, but his strength would allow him to overpower opponents at the net with aggressive volleys. He'd likely excel at blocking powerful shots and turning defense into offense.

Special Shots: Knuckles' special shots could be themed around his abilities. One could be a powerful "Spin Dash" shot, a super-charged groundstroke that sends the ball hurtling across the court with extreme speed and unpredictable spin. Another could be a defensive "Glide" maneuver, allowing him to quickly cover the court and retrieve seemingly impossible shots. A third could be a "Chaos Emerald Power" shot, a high-risk, high-reward shot that, if successful, could result in an instant point.

Weaknesses: Knuckles' slower speed and less precise shots would be his primary weaknesses. He would be vulnerable to quick, agile opponents who could exploit his slower movement and force him into defensive positions. His powerful shots, while effective, would also be prone to errors if not executed perfectly. He would need to rely on his power and strategic positioning to compensate for his lack of speed and precision.

Overall Playstyle: Knuckles would be a high-risk, high-reward character. Players using him would need to be strategic, utilizing his power effectively while mitigating his weaknesses. His playstyle would be less about finesse and more about overwhelming opponents with raw power and strategic positioning. He would be a formidable opponent for those who can master his unique abilities, but a challenging character to learn for those accustomed to faster, more precise characters. His inclusion would add a welcome layer of strategic depth to the game.