Juan Cruz pitches in relief for the Kansas City Royals. In 2009, he lost his ability to strike out batters at a high rate, coming in at 6.8 per 9 innings compared to 9.1 per 9 innings for his career. That raised his hits per nine, and with a high career walks per 9 he ended up with a 5.72 ERA for the season.

According to FanGraphs, Cruz did not lose any velocity off his fast ball, but used it a lot less. He introduced a cutter, and my guess is that just didn’t work.