Clearing the bases: Concerns about Castro

First base: How good is Starlin Castro? One thing we preach a lot about here on the SweetSpot blog is a hitter's ability to take walks. Two reasons this is important: One is the practical analysis that it helps your on-base percentage, which helps your team's offensive production; but a better approach can also make a player a better hitter (see how Mark Trumbo's improved patience has helped him this year). Which gets us to Cubs shortstop Starlin Castro.

As a 20-year-old rookie in 2010, he hit .300 with a .41 BB/SO ratio (29/71). He didn't walk much and only hit three home runs in 463 at-bats, but he hit 31 doubles and how many 20-year-olds can hit .300? Last season, he hit .307, led the NL with 207 hits and had a .36 BB/SO ratio (35/96). His isolated power improved from .108 to .125. It wasn't a big step up, but still nice numbers for a 21-year-old shortstop.

In 2012, his power has continued to improve slightly as you would expect -- his ISO has increased from .125 to .138. But his walk rate has plummeted. He has six walks and 43 strikeouts, which puts him on pace for season totals of 16 and 116. While he's hitting .308, his on-base percentage is just .320. The overall package means he's barely improved as a hitter: His wOBA as a rookie was .325; it's .331 in 2012.

Unlike Trumbo, Castro is swinging more, not less. After swinging at 32.7 percent of pitches outside the strike zone in 2011, that number has jumped to 40.6 percent. His overall swing rate is up and his contact rate is down. His inability to control the strike zone appears to be limiting his development as a hitter. There are guys, like Kirby Puckett or Vladimir Guerrero, who were still great even though they expanded the strike zone. But those hitters are rare. The fact that Castro's production isn't improving raises the question of exactly how valuable his bat will be long-term. Look, he's a good player right now, don't get me wrong: Not many shortstops can hit .300 with some power. His defensive metrics at shortstop are vastly improved, even if he's still having his share of brain cramps in the field.

But right now, he's not a No. 3 or 4 hitter on a championship team. And if the Cubs are going to build a championship team in the future, I don't believe Starlin Castro is going to be the best player on that team.

Second base: Terrific Trout. Mike Trout continues to rake, going 2-for-4 with a home run, walk and stolen base in the Angels' 3-2 victory Monday over the Dodgers. He has 15 steals since his recall, most in the majors. He's hitting .354/.412/.565. Maybe he is the best player in the American League. Trout's home run came off a Chris Capuano curveball, and his ability to hit that pitch has been a key in his improvement from 2011. Last year, he swung at 29 curves and missed on eight of those pitches; this year, he's swung at 21 curves and missed just once.

Third base: Don't look now ... The Yankees have won four in a row, eight of 10 and are 14-4 since falling to 21-21 on May 21. Ivan Nova pitched seven scoreless innings in Monday's 3-0 win over the Braves, a victory that pushed the Yankees into a first-place tie. After allowing a .313 average through his first 10 starts and allowing at least one home run in nine of those starts, Nova has allowed a .148 average and no home runs his past two outings.

Home plate: Tweet of the day.