Theriot claims his ground, but Castro coming on fast

Ryan Theriot is the Cubs' shortstop - for now.

How long "now" lasts depends on a couple of things. Check that. It really depends on how fast phenom Starlin Castro comes along.

Based on spring training so far, Castro is coming on fast. He homered in Thursday's victory over the Padres and entered Friday 8-for-14 (. 571) in the Cactus League.

Earlier this spring, Theriot said Castro would have to "come get" the shortstop job. Maybe it's a challenge Theriot will regret issuing.

To be fair, Theriot has done a creditable job, despite a comedown season in 2009 from a career year in 2008.

How will it shake out? Let's look at the factors.

The age factor: Much has been made of Castro not turning 20 until March 24. Setting that aside for a moment, the bigger issue is that Theriot already is 30, and that any decline in numbers at that age will raise concern.

Theriot came to spring training looking to be in great physical shape, and some of his statistical decline may have come from manager Lou Piniella wanting him to "drive" the ball more last season. Theriot also wears down in September - he batted .240 over the final month of last year; in 2007, his average was .202 for that period - even as Piniella has promised to get him some rest.

Theriot's on-base percentage fell from .387 to .343 from 2008 to 2009. His walks decreased from 73 to 58 while his strikeouts spiked from 58 to 93.

As far as Castro being "too young," Piniella doesn't seem to think that matters.

"The amazing part about it is these special-type players, they're ready to play at the big-league level at a much younger age," Piniella said. "Usually, the age for big-league players is about 23, 24. When you're really good, you can get to the big leagues at 19, 20 and make a really good showing for yourself."

The leadoff factor: As it stands now, Theriot will be the primary leadoff hitter, with right fielder Kosuke Fukudome getting some time in the No. 1 slot.

As it also stands, the Cubs really don't have a true leadoff hitter.

Theriot will need to up his OBP. As far as stealing bases goes, it has not been an effective weapon in Theriot's game. He was 21-for-31 last year, good for 68 percent. Most stats people say a baserunner needs to be at 75 percent to make the reward worth the risk.

Theriot also would be well served to getting back to the things that helped him have a career year in 2008, when his flyball rate was 20.2 percent. Last year, that rate rose to 30 percent, and with Theriot not being a power hitter, many of those flyballs settled into fielders' gloves.

The experience factor: The Cubs want Castro to play every day, so that most likely means he'll open the season at Class AAA Iowa. The team does not feel having him as a big-league backup will do him any good.

Castro played in 51 Rookie League games in 2008, so last year was his first full year of pro ball in North America.

At Class A Daytona, Castro batted .302 with a .340 OBP and 3 homers. At Class AA Tennessee, he batted .288 with an OBP of .347 and no homers.

The need factor: If Theriot shows his 2008 season was a fluke - Theriot's OBP in 2007 was just .326 - and Castro tears it up in Iowa, there will be huge pressure to bring the kid to Chicago.

That might not be the worst situation for the Cubs. Theriot can spell Castro at shortstop and perhaps even shift to second base, where the platoon of Mike Fontenot and Jeff Baker still must prove itself.

NL's bestWhere we rank the top shortstops1. Hanley Ramirez, Marlins2. Troy Tulowitzki, Rockies3. Yunel Escobar, Braves7. Ryan Theriot, CubsFalse18172000Cubs' Ryan Theriot slides safely into second with Milwaukee Brewers' Joe Inglett covering.Associated PressFalse