"I felt good," Zambrano said. "I was strong. I kept the ball down. I kept every pitch down. The last inning, the second inning, I was rushing too much, but I was able to come back and get the last out."
Zambrano spent last season with the Marlins. The 31-year-old, who is currently a free agent, was 7-10 with a 4.49 ERA, 95 strikeouts and 75 walks in 132 1/3 innings.
"I have a couple of offers, but they're not the kind of offers that I want," Zambrano said. "I think this is a good moment, the WBC, to show or prove something."
At his peak, Zambrano was one of the game's best pitchers. He had five straight seasons with 200 or more innings, topped 200 strikeouts twice and posted a 2.75 ERA in 2004. Zambrano's faded in recent years, though, and he hasn't topped 150 innings since 2009.
Matthew Leach is a writer for MLB.com. Read his blog, Obviously, You're Not a Golfer and follow him on Twitter at @MatthewHLeach. This story was not subject to the approval of Major League Baseball or its clubs.