The Knicks now have 19 players under contract heading into training camp, which starts Oct. 2. Thirteen of those 19 players have guaranteed deals. NBA rules stipulate that teams can have 15 players on the opening-day roster.
So Shurna, Bellfield, Sims and Thompson will have to impress the Knicks' staff in training camp to gain a roster spot.
Bellfield played four seasons at UNLV, where he became the Mountain West Conference's all-time assists leader (582).
Sims, 6-10, averaged 11.6 points and 6.0 rebounds as a Georgetown senior.
Shurna set Northwestern's all-time scoring mark with 2,038 points.
Thompson, from Pepperdine, appeared in five games (three starts) for the Cleveland Cavaliers last season.