curve

behind (or ahead of) the curve behind (or in advance of) the current trend.

☞ The expression is probably based on the notion of the curve of a graph.

2005Stylus Magazine Everyone knows the cultural stereotype-the Japanese are hopelessly, adorably behind the curve when it comes to Western music styles.

throw a curve cause confusion or consternation by acting unexpectedly. US informal

☞ Curve is short for curve ball, a term in baseball for a delivery in which the pitcher causes the ball to deviate from a straight path by imparting spin.