Pro No. 2: Rudy provides the San Antonio Spurs veteran leadership
The Spurs roster has steadily gotten younger in recent seasons and figures to be even younger next season. While Gay may not necessarily fit with the Spurs youth movement, his experience and leadership could be useful.
Rudy appears to have taken players like Dejounte Murray, Lonnie Walker, and Keldon Johnson under his wing and has spoken highly of their development in the past. Were he to return next season, he could continue to serve as a mentor to younger players on the roster, particularly guys like Vassell. His valuable insight could even aid their development.
Con No. 2: Retaining Gay blocks Luka Samanic from getting minutes
Rudy's return would have a direct effect on former 2019 first-round pick Luka Samanic. Samanic has shown flashes in limited minutes, and after two seasons spent developing, Luka should have a spot in the rotation. With Rudy on the roster, that's unlikely to happen.
That said, with Luka getting better and Gay possibly declining, it seems inevitable that Samanic would surpass Rudy at some point. Next season could serve as a transition year for San Antonio. Were that the case, it could make sense to replace Gay in the rotation with Luka sooner rather than later.
Pro No. 3: Rudy fills a need at power forward
San Antonio has limited depth at power forward but may seek to bolster the position in the NBA Draft or free agency. That's said, San Antonio could also opt to bring Gay rather than look for a replacement.
After all, the Spurs know exactly how Rudy fits within their system as opposed to a new player. There is always the possibility that a free agent doesn't fit, as was the case with former short-lived Spur DeMarre Carroll.
Rudy has provided the Spurs with a reliable stretch four option since joining the team. Given San Antonio's lack of shooting this season, losing Gay could have a surprisingly negative effect on the team's spacing next year.
After all, San Antonio opted not to re-sign Marco Bellineli and Bryn Forbes last off-season. That decision affected the Spurs this season, as evidenced by the team's 3-point percentage dropping from 37.6 to just 35.0.