VIERA, Fla. -- When he's off the field, Nationals right-hander Jordan Zimmermann hangs out with catcher Luke Montz. The two are currently roommates and have been friends since last year, when they played for Double-A Harrisburg.

What kind of person is Zimmermann when he is away from the field? He loves to talk and tell jokes. Zimmermann's also an avid golfer: He and Montz often go to the driving range to practice their swings.

"He has a mind of his own, talkative," Montz said. "We watch TV together. He is outgoing. He is very fun to be around."

One would never know that Zimmermann is a talkative person when he is at Space Coast Stadium. He is all business on the mound and shy when he talks to the media. It's almost like he is in another world.

"He goes in there with a totally different mind-set," Montz said. "He is a bulldog out there. Once Jordan picks the ball up and knows he is starting that day, he has a mind of his own. He is in the zone and is ready to throw.

"When he is in the bullpen, he is so serious. Jordan has one thing in mind, and that's to win the ballgame and do the best he can on the mound. He is not worried about anything else."

So far, Zimmermann, 22, has lived up to the billing of being the Nationals' best pitching prospect. On Tuesday afternoon, he was on the mound against the Mets, and he didn't give up a run in 3 1/3 innings of what ended as a 5-5 tie.

In three Spring Training starts, Zimmermann has pitched 8 1/3 innings without yielding a run, while striking out 10 and walking two.

In his first two starts, he faced a combined 15 batters and retired all of them. In Tuesday's start, however, Zimmerman was tested, but he proved that he could get out of jams. In the first inning, the first two Mets hitters -- Cory Sullivan and Marlon Anderson -- reached base. But Zimmermann was able to get out of the inning by retiring the next three hitters.

Zimmermann had an easy second inning, but struggled in the third frame. With one out, Zimmermann walked Sullivan and allowed another single to Anderson. But he induced a double-play ball from Rob Mackowiak to end the inning. Zimmerman left with one out in the fourth inning after reaching his pitch limit.

"I got myself in a couple of binds early," Zimmermann said. "The Mets fought off a lot of pitches. Unfortunately, I wasn't able to go four innings. I got a crucial ground ball [in the third inning] that saved me a lot of pitches. I don't know. I guess it was a pretty good day.

"I needed [to show that I could get out of trouble], I guess. I really had to battle today. It was pretty hot out there."

Pitching coach Randy St. Claire said Zimmermann didn't have his fastball command on Tuesday, but was pleased that Zimmermann was able to make pitches when it mattered the most.

"I didn't see him try to do more [on the mound]," Claire said. "He just kept going after it without his best stuff. I didn't see him get flustered. He is going to need to do that.

"He needs to execute pitches and get out of jams. It's not always going to be one-two-three. He showed me that poise, that character I see in him. That puts him very high on the scale."