They're friends, rivals and roommates -- as well each other's biggest fans -- as they vie for each other's job.
"We've gone through a lot of ups and downs together," Johnson said. "We got to the big leagues right around the same time, and we've gone through this whole thing together. We're pretty good friends and we're definitely rooting for each other, though this spring it's a little different. We still hope for the best for each other."
Johnson, 27, has played exclusively at third base in his brief time in the Major Leagues, but he played first base in college and as recently as 2007 in the Minor Leagues. Wallace, 25, has played only first base since getting called up in 2010, but he played third base in college and early in his Minor League career.
The pair has been working out at both first and third base this spring, often alongside each other, and hanging out in the evenings at the house they share. They eat dinner together, catch the occasional movie and even talk occasionally about their on-field battle.
"We live together, so it's definitely a lot of fun," Wallace said. "We mess around with each other a lot. We always joke around about it and stuff. We're pulling for each other and want this team to win. We both feel we can help the team win. If it's me at first and him at third, or vice versa, it's not as big of a concern as it is helping [with] turning this thing around."
Johnson burst onto the scene in 2010 and hit .308 with 22 doubles, 11 homers and 52 RBIs in 94 games, en route to being named the team's rookie of the year. He was the established starter at third entering 2011, but wound up getting sent to Triple-A at the end of July after hitting .245 with six homers and 36 RBIs.
Wallace, acquired by the Astros at the Trade Deadline in 2010, got off to a terrific start at the plate last April, but slowly watched his average decline. He joined Johnson in getting sent to the Minor Leagues in late July, after hitting .268 with four homers and 26 RBIs.
Both came back to the Major League club when rosters expanded in September, but Carlos Lee was entrenched as the starter at first and rookie Jimmy Paredes had taken over at third. Wallace and Johnson suddenly had to prove themselves again.
"We've definitely had a lot of similarities," Wallace said. "When we went down [to Triple-A], we drew closer together. We were really good friends, but we talked some things out and figured out some stuff [about] what we needed to do and go about our business, and I think we drew closer in that sense. We knew we could rely on each other to push each other. Now, playing similar positions, they're having us do both [first base and third base], and we kind of challenge each and push each other."
When Grapefruit League games began, Wallace started at first base and Johnson at third base on Saturday, and Wallace was in the lineup at third base and Johnson at first the next day. Manager Brad Mills said Wallace will see more time at third than Johnson will at first as the spring progresses.
"My first priority is definitely to win the third-base job," Johnson said. "But if I can add some versatility to my game, then I'm all for it."
Getting a chance to play third base again hasn't been too big of a challenge for Wallace, who lost about 15 pounds this offseason.
"The angles are the exact opposite," Wallace said. "At first, we're going to the right most of the time -- and at third, we're going left most of the time. It takes a day or two to really get out there and get that feeling and rhythm going the other way. Every week, I feel a little bit better."
What would really make both Johnson and Wallace feel better is to break camp on the 25-man roster in a month. With Matt Downs, Angel Sanchez and Rule 5 Draft pick Marwin Gonzalez among those in the infield mix, it will be an uphill challenge. But they'll go through it together.
"Being able to go through ups and downs with somebody brings you closer and makes you better friends," Johnson said. "We're kind of feeding off of that right now and helping each other out, and we both want to make sure [getting sent to the Minors] doesn't happen again."