catch a falling knife
v. phr.— «The question for Mr. Marks and others is when to start buying in earnest. Early buyers risk “catching a falling knife,” in market parlance, if prices keep tumbling. But late buyers risk losing out on the best deals and the best returns. “We think we have to catch a falling knife,” Mr. Marks said.» —“Finding Potential for Debt in Distress” by Norm Alster New York Times May 25, 2008. (source: Double-Tongued Dictionary)