© 2013 MLB Advanced Media, L.P. All rights reserved.

5/7/2013 9:41 P.M. ET

Castro has come a long way in three years

CHICAGO -- Tuesday marked the third anniversary of Starlin Castro's callup to the big leagues. On May 7, 2010, the shortstop was promoted from Double-A Tennessee to the Cubs and hit a three-run home run in his first at-bat in Cincinnati.

Since that day, Castro, 23, leads all National League players with 477 games played and is tied for sixth among big league shortstops with 200 RBIs in that span. His 567 hits since his debut lead the NL and rank fifth-most in the Majors. Detroit's Miguel Cabrera leads all players with 587 hits in that span. Castro's 101 doubles since his debut rank seventh-most in the NL.

The shortstop entered Tuesday's game having hit safely in 25 of his 29 games. He also had a 14-game hitting streak from April 6-22, and batted .317 in that span.

Does Cubs manager Dale Sveum see progress with Castro?

"There's progress since the day he got here," Sveum said, "but I think it's still a work in progress with some mental things at shortstop. If he wants to get to another level swinging the bat, there's still a lot of improvement that can happen there to get the OPS higher. It comes and goes with him as much as anything. There's still quite a bit of improvement that can happen on both ends."

Part of the adjustments that need to be made involve Castro's timing at the plate.

"He has such unbelievable hand-eye coordination," Sveum said. "He fouls a lot of balls off and does a lot of things. He has to take advantage of hittable fastballs."

Valbuena steps in, now entrenched at hot corner

CHICAGO -- The Cubs projected Ian Stewart as their starting third baseman, but Luis Valbuena has taken control of the spot.

"I would never have any problem playing him every day, because his at-bats against left-handers are pure and he sees pitches and doesn't swing out of the zone against left-handed pitching," Cubs manager Dale Sveum said. "He's obviously an everyday player. He's one of the most productive third basemen in the game right now."

Valbuena ranks fourth among National League third basemen, batting .271 heading into Tuesday's game, and trailed only the Reds' Todd Frazier in home runs. The Giants' Pablo Sandoval leads all NL third basemen in RBIs.

What Sveum likes is that Valbuena, a left-handed hitter, gives a quality at-bat. He stayed busy over the winter, playing in Venezuela.

"Those kind of experiences help anybody," Sveum said. "I don't think guys do enough of that any more. A lot of people say they're tired and don't want to play winter ball or instructional league. The more baseball you can play as a younger player, the better you're going to be. That's just like the walk of life."

Valbuena tied his career high with three hits Friday and Monday. He hit four home runs in 265 at-bats last season, and already has hit five this season.

Stewart missed all of Spring Training because of a strained left quad suffered in the first intrasquad game, and he was optioned to Triple-A Iowa on Saturday.

Extra bases

• Kyuji Fujikawa's second rehab outing scheduled for Tuesday was pushed back one day because Double-A Tennessee's game was called because of rain after five innings.

The Smokies fell, 16-0. Fujikawa did not get in the game and will pitch on Wednesday.

If all goes well, the right-hander will join the Cubs in Washington D.C. for their weekend series against the Nationals.

Fujikawa has been sidelined since April 13 with a strained right forearm and pitched one inning in a rehab outing Sunday for Triple-A Iowa.

• Anthony Rizzo was batting .439 with seven doubles, three home runs and 11 RBIs in his last 11 games, and has raised his average from .173 on April 25 to .262.

"The bottom line is you just get more comfortable," Sveum said. "Coming out of Spring Training, it's totally different how pitchers will start pitching you, and you'll see a lot more breaking balls as the season goes on, which you don't see much of in Spring Training, and you see different kind of pitchers. It's just getting your at-bats and getting better pitches to hit, for one. He's still a little bit aggressive, but right now he's taking advantage of mistakes he's getting."

• Cody Ransom is the only backup infielder on the Cubs' roster, and he's been getting some extra work at first base in early batting practice. Rizzo is the regular, but the Cubs don't have a backup.

"You never know if [Ransom] will get over there one day," Sveum said. "Hopefully not. Especially the way Rizzo is swinging against left-handed pitching. It's a just-in-case thing."

• Right-handed pitcher Cory Wade, who was pitching for Triple-A Iowa, was released, the Cubs announced. In 16 innings over 10 games at Iowa, Wade gave up 14 runs on 28 hits and walked seven while striking out 16.

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.