So where does Martinez fit it? It probably depends on how well he swings the bat.
"In my eyes, I always look at competition as I'm competing against myself," Martinez said. "I feel like I don't compete with anyone else. I just worry about myself and what I can do and what I can control, and whatever happens, happens. That's all I can do."
Martinez is only 25, but he is no longer a prospect. He burst onto the scene in 2011, making the jump from Double-A to the Majors before replacing Hunter Pence in the lineup following his trade to the Phillies. He had hit at every level of the Minor Leagues and had an impressive debut as a rookie, but last year was nothing short of a struggle.
After beginning the season as the Opening Day left fielder, Martinez wound up hitting .241 with 11 homers and 55 RBIs and spent a month toward the end of the season in Triple-A. The pressure built with each at-bat, and Martinez had a hard time dealing with failure.
"It was definitely tough, but it was a learning experience," he said. "I feel this year my head is more clear. I don't look at each at-bat so intensely. Bad at-bats happen, and you can't let it snowball. If you had one bad at-bat and you look at it deep and you look at the next one, before you know it you're behind already. I felt like I was putting a lot of pressure on myself."
Martinez, who still managed to lead the team in RBIs, felt a burden to drive in runs. He admits he tried to hit home runs on too many occasions last year, feeling the pressure to be a primary run producer like he did in the Minors. This year, his focus is solely on driving the ball to right field.
"I've always put my average in front of my power numbers because of my size and the ability God has blessed me with, when I hit it well it does go," he said. "That's what I'm concentrating on this year. That's it."
The surgery that Martinez underwent at the end of last season to remove the hamate bone in his left hand put him behind schedule entering the spring. He didn't get to take as many swings as he normally would have, but he's trying to make up for lost time with new hitting coach John Mallee.
"We spent a lot of time in the video room and a lot of time going over his swing and he tried to tell me what things he does well and where he struggles," Mallee said. "I was able to explain to him how the swing works and, more importantly, how his swing works."
Mallee has been working with Martinez to shorten his swing. The hitting coach says Martinez launches his hands high, which makes for a longer path to the ball. He's shortened up the depth of his launch and the height of launch to make him shorter and quicker to the ball.
Mallee believes Martinez has the intangibles to be a good hitter. He recognizes pitches well and has good bat speed.
"It's all going to come down to his approach," he said. "The difference in him being more consistent this year is not going to be mechanics. It's going to be approach."
The Astros are giving Martinez some time in right field this spring, knowing he'll need to be able to play more than one position to make the team. In the offseason, he worked with Cardinals outfielder Jon Jay in Miami to become a better defender.
The team hasn't lost faith in Martinez's abilities, even if it brought in some players who are trying to take his job.
"It was probably a little bit of a wakeup call going to Triple-A, but he got some things sorted out," Luhnow said. "The No. 1 thing for J.D. is making sure he's healthy and doesn't have any pain swinging the bat. ... He's got a plus arm, we know that. He's got a plus power bat. He'll be given every opportunity to win a job as well."