Martinez was limited to seven innings during spring training while rehabbing a toe injury. He knew his command wouldn't be sharp right away.
In six innings, Martinez gave up five runs on four hits and five walks. He hit three batters.
"I felt great, but I'm not pitching right now," Martinez said. "I'm throwing right now. It will take time."
Martinez has a reputation for going inside, but the three hit batters were more indicative of wildness than headhunting, he said, emphasizing he wasn't going after Jose Guillen, who was plunked twice.
"I know he was upset, that wasn't my intention," Martinez said of the incident in the fifth when after he hit Guillen a second time, the Nationals outfielder tried to go out to the mound but was restrained by catcher Paul Lo Duca.
REPLAY: Carlos Beltran's first homer of the season helped the Mets beat the Nationals 10-5 Thursday night, but what happened in the aftermath could have a greater impact on the team this summer.
Beltran, who struggled last season in the first year of his $119 million contract, was booed on Opening Day after going 0-for-4, and initially he didn't want to take a curtain call. However, after prodding from veteran Julio Franco, Beltran took a brief bow.
Franco, 47, the oldest player in the major leagues, knows enough that it doesn't pay to make an enemy of the crowd, and the prudent thing is for Beltran to accept the cheers when they come.
Zambrano was scratched from his first start on Wednesday with a tight left hamstring.