Underperforming: Jericho Sims
Admittedly, judging Jericho Sims based on his production so far this season is tough. He's played in only 18 games, averaging 1.3 points and 1.4 blocks. He missed time with an ankle injury he suffered in December, but even outside of that, Sims hasn't been a regular face in the rotation.
When Robinson went down, Sims was initially the starter before being replaced by Hartenstein. The Anunoby trade on Dec. 30 brought Achiuwa to New York, and since the former Raptor made his debut, Sims has played in only four games. He's combined for only 12 minutes in those contests. He's faded into the background, as the last time he played was on Jan. 9.
Sims was never expected to play a large role in Thibodeau's tight rotation, but seeing more of him would be nice. You never know what version of Achiuwa you'll receive, so it'd benefit the Knicks if Thibs would turn to Sims more, at least until Robinson returns (if he does). Developing Sims shouldn't be pushed to the side because Achiuwa may or may not go on to be the Hartenstein replacement.