Pitcher Carlos Zambrano left Sunday night's start against the Mets after three innings because of tightness in his lower back. Zambrano threw 80 pitches and departed trailing 4-0. He gave up two earned runs and four hits. An All-Star last season, the 24-year-old right-hander entered 8-4 with a 3.24 ERA in 22 starts this year. He won his previous four decisions and had lasted at least seven innings in his past seven starts. Michael Wuertz took over for the Cubs in the fourth.