It was all done with the hopes of resurrecting his career and winning a spot on the Astros' Opening Day roster.
"I feel like this is very important," Martinez said. "I'm confident that if I go out there and I do what I know how to do and I get the opportunity, that I'll have a good chance. It's just getting out there and being able to do what I know how to do, and that's the biggest thing."
Martinez, 26, hasn't quite been able to match his strong debut, when he hit .274 with six homers and 35 RBIs in 53 games as a rookie in 2011 after coming straight from Double-A. He played in just 86 games last year, missing more than a month of the season with a wrist injury. He batted .250 with seven homers and 36 RBIs, and he was later removed from the 40-man roster.
As prospects like George Springer emerged and L.J. Hoes came aboard from the Orioles, Martinez knew he had to play winter ball to post some numbers. He batted .312 with six homers and 18 RBIs in 24 games in Venezuela. The experience was a good one, even though he lost 16 pounds because of sickness.
"I went down there to work on trying my new swing, what I've been working on all offseason," he said. "Venezuela is supposed to be one of the better leagues to go, and that's where I wanted to go off the bat. I really just enjoyed playing down there. It was fun. They had good baseball, and the fans were great. It was an experience I'll never forget."
In the offseason, Martinez studied video of his swing with the goal of trying to get the bat to stay in the zone longer. A similar change helped Castro blossom into an All-Star last year, and Martinez noticed the results.
"The way it hit me was when I saw the slow-motion video and looked at how many frames -- I call them clicks -- when your bat is in the zone, and you watch some of the great hitters and they're in the zone for six, eight clicks and you're like, 'Wow,'" he said. "I was in the zone, at my best, two or three clicks.
"I looked at guys like Jason and [Jose] Altuve and the adjustments they made, and they're in the zone five to six [clicks]. There it is. If you're in the zone longer, you have more margin for error. That's really all I worked on the entire offseason and getting some kind of rhythm into it."
Astros hitting coach John Mallee said Martinez's swing was too sloped, which didn't allow him to get on plane with the pitch and stay there. Mallee lowered his hands at his launch and did different things to help him get on plane with the pitch sooner, helping his bat stay in the zone longer.
"He wants to be good at it, he wants to master something," Mallee said. "What happened was the ball was going down, and he was hitting the top of the ball and cutting a lot of balls and wasn't getting to his true power.
"You want to get on plane to the pitch, and to hit the ball with backspin you have hit through the ball and stay on plane. That way you get lift to it, as opposed to hitting down on it and cutting through it. Now that he's on plane, pitches he's not on time on, he's still on the same plane as the pitch, so he can catch it in different parts of his swing and still square the ball up and make solid contact."
The results so far in Spring Training have pleased Martinez.
"I feel great," he said. "I feel like I'm hitting the ball. I feel like my bat's in the zone a lot longer, and I feel like I'm hitting the ball harder. I'm using more of my legs now, where I was more upper body last year, and I was more east to west. I feel like now I'm more north to south with my entire body."
Astros general manager Jeff Luhnow says Martinez understands he'll have to have a good spring to make the club, and the extra work he's put in with his swing is a good sign.
"He's very eager to work himself back on the 25-man roster," Luhnow said. "He understands what happened the last couple of years. He was fortunate enough to go straight from Double-A to the big leagues, but sometimes that can be a blessing more than a curse, because he is missing some development time in Triple-A other guys tend to get. But I'm confident, given the work he did this winter and everything, he's got as good a shot as any to make the club."