Gilbert, who has been dealing with a groin injury, was out for four of the past seven games for Iowa State (24-9).
The absence of Iowa State's team leader in points (13.4), assists (4.1), and minutes played (31.6) will leave a big hole in their starting five for the rest of the NCAA tournament.
Iowa State is set to take on 14th-seeded Lipscomb on March 21st at 1:30 p.m. Eastern time (New York) and will air on TNT.
The six-foot-four Senior will, unfortunately, have to spend the rest of his final season on the bench cheering his team on as they try to make a title run a three-seed.
If Iowa State beats Lipscomb, they will face the winner between (#5) Ole Miss and (#11) San Diego State/University of North Carolina (play-in game on Tuesday, March 18th).