3. Luka Samanic
Starting off the list is the 19th pick from the 2019 NBA Draft, Luka Samanic. With his dynamic shooting, the Croatian prospect impressed a lot of scouts before he got drafted. When the Spurs drafted him, they needed a big who was capable of stretching opponents' defenses.
Looking at his stats from when he was still playing overseas, it looked like he would fit right in with the team, especially his performance in the U18 Euro Championship A in 2018. In it, he averaged 17 points, 7.7 rebounds, and 1.8 blocks on 48% FG and 47.4% from 3-point range.
Immediately after getting drafted, the Spurs sent him to their G League affiliate, the Austin Spurs, back in October 2019. While he did perform well there, averaging over 15 points, 7.8 rebounds, and 1.8 assists, he did it with below-average efficiencies. Shooting 44% overall and 30% from the 3-point area won't get you called up in the NBA.
That was true for Samanic, as he would get called up by the Spurs in February 2020. Samanic would get to play only one NBA game before the season got shut down because of the COVID-19 pandemic. Together with the NBA Bubble games, Samanic finished with 5.3 points, 3.3 rebounds, and 2.0 assists.
The following season, Samanic would average fewer points, rebounds, and assists while playing more games than the previous year. Not to mention, he shot worse from the 3-point line, going from 37% to 27%. Also, Spurs fans criticized his lack of effort to improve his game on both ends.
He never became the modern big the Spurs wanted him to be, and maybe the organization was too impatient with Samanic. In just two seasons with the Spurs, the team had enough and decided to waive him in October 2021. At least the Spurs got a steal in Keldon Johnson during the same year they got Samanic, so I guess it worked well?