MESA, Ariz. -- For the first time since his freshman year in high school, Javier Baez started at second base. Could it be a sign that the Cubs are trying to find a spot for their top prospect?

Baez, 21, is projected to open the season as Triple-A Iowa's shortstop, but he was at second base in Monday's split-squad loss to the Athletics.

"I'm just ready for anything," Baez said before the game. "I just want to play second."

Cubs manager Rick Renteria didn't want to miss Baez's debut at second, so he went with the team to Phoenix.

The Cubs committed to Starlin Castro as their shortstop in August 2012, signing him to a seven-year, $60 million contract. Baez was the team's first-round pick in the 2011 First-Year Player Draft, so the question has been how do the Cubs fit both talented shortstops in the same big league lineup? Moving Baez to second base may be the answer, although Renteria tried to downplay the switch.

"I don't know if that's the case in terms of him being closer [to the big leagues]," Renteria said. "It makes sense for us to be able to move him around. Hopefully, before the spring is out, we'll see him at third base, too. Right now, we'll give him a couple days, back to back, at second base and go from there."

On Monday, the Cubs matched Baez up with Gold Glove second baseman Darwin Barney, who started at shortstop.

"I'm pretty sure he'll help me and tell me how to play it," Baez said.

Castro didn't think Baez would need much time there to feel comfortable.

"It's easy -- first base is right there," Castro said. "When you're a shortstop, you can play any position in the infield. He'll be all right."

Baez didn't have any problems in the loss. He made his first defensive play in the second when he caught Alberto Callaspo's popup, and handled a groundout by John Jaso in the third.

Baez and Barney combined on a fielder's choice to get Brandon Moss at second, and turned an inning-ending double play in the fifth.

"That nice double play with Barney [in the fifth] on the hard-hit ball that actually carried him through the middle, ended up coming across the bag toward the shortstop side, with a long throw back to first, which was pretty impressive," Renteria told reporters in Phoenix after the game. "Nice job."

Did Baez look comfortable?

"Yeah, he looked fine over there," Renteria said.

Baez, the Cubs' top prospect and No. 7 overall according to MLB.com, has been working with infield coach Gary Jones early most days in camp so he can learn the different angles and footwork needed.

"He's been working quite a bit on his pivots and things of that nature," Renteria said. "The biggest concern for anybody when you move to a new position, especially at second base, is the pivot, and making sure they're in and out of there on the turns. ... It's not an easier position, by any means. It has its own nuances. We'll see how he looks, how it sets up."

On Sunday in Las Vegas, Baez was taking more grounders at second. It's all part of the development process.

"The biggest thing is we were trying to get him to come through the ball a little bit more," Renteria said of the extra work. "Sometimes he has a tendency to get a little flat-footed at shortstop so Jones has been working with him quite a bit.

The Cubs front office has been insistent that Baez will open this year in the Minor Leagues, but if he can show his versatility, that may expedite his promotion to the big leagues.

"I'm just trying to get there and be in the lineup," Baez said.

Last spring, Baez batted .298 in 17 spring games, and belted four home runs, including two more in an exhibition game against a Japanese team. This year, he's hitting .281 with three home runs after going 1-for-3 on Monday.

"For us, we're watching him this spring, and he's adapting from at-bat to at-bat, which is a good thing," Renteria said. "He might strike out on three breaking balls in the first at-bat and come back and put together a six, seven, eight, nine pitch at-bat where he's fighting pitches off and doing things he should be doing in terms of grinding at-bats out.

"Again, time will tell us where he's actually at in terms of that maturity process. He's shown the ability in short stints here in the spring to be able to adapt and adjust."

In high school, Baez said he preferred playing second over shortstop. He just needs to re-learn the different angles, and go from there. He also played center field and was a catcher in high school. He probably won't have to catch in the big leagues.

"I don't think so either," Baez said.