Palace lost away from home in the Premier League for the first time since October, with Leeds' Dominic Calvert-Lewin scoring twice, both goals coming after long throw-ins.
Justin Devenny's late penalty offered a consolation, but the scoring was completed by Anton Stach's free-kick in the dying seconds.
Glasner said his team struggled with the basics on a tough night at Elland Road, but added that he trusted his current group of players to respond in the right manner.
"It's like we were not sharp enough," he told his post-match press conference. "If you defend the set-plays like we did today, you have no chance to get a point in the Premier League.
"That's why at the end we lost and conceded all these goals. You have to win your duels. [Christantus] Uche did it at the end and all of a sudden we have a penalty.
"It's football, sometimes you can reduce it to the basics, and in the basics we were not good enough."