Ten St. Louis Cardinals stats to watch in 2015

The St. Louis Cardinals defeated the Chicago Cubs on opening night 3-0. It was great to see Jason Heyward collect three hits in his Cardinals debut, Adam Wainwright overcome some sticky situations to blank the Cubs over six innings of work, and the Cardinals knock Chicago's $155 million ace Jon Lester out of the game before the end of the top of the fifth. All in all, a nice start to the season. But it's just one of 162 contests this 2015 campaign so let's have a look at ten stats I'll be monitoring as the season unfolds.

Catcher: Wins Above Replacement (WAR)

Here's how many Fangraphs WAR (fWAR), the Cardinals have received from the catcher position in each of the last five seasons:

• 2010, 2.8
• 2011, 4.5
• 2012, 6.2
• 2013, 4.8
• 2014, 1.9

As a part-timer in 2013, Matt Adams put up a very impressive batting line: .283/.335/.503 (.365 wOBA, 135 wRC+). Most impressive was the power Adams displayed. The stat Isolated Power (ISO) is one that excludes singles and focuses solely on a player's extra-base hits. In 2013, Adams posted a healthy .220 ISO that was comfortably above the MLB overall rate for non-pitchers of .148 and first baseman of .178.

Last season, Adams saw his offensive production sag in his first full year as a primary position player. He hit .288/.321/.457 (.337 wOBA, 116 wRC+). Adams hit for a .169 that was 51 points lower than his 2013 ISO. Adams's 2014 ISO was about average for MLB first basemen, who posted a .167 ISO as a group. Adams flashed more power capability in 2013. Will he be able to tap it once again in 2015?

Second Base: BB%

The Cardinals selected Kolten Wong at the end of the first round in the 2011 MLB amateur draft in part because he was a polished hitter expected to move quickly through the organization. Wong did just that. As a minor-leaguer, Wong hit for a collective minor-league slash line of .305/.367/.451. That .367 OBP is handsome and due in part to a high BA and a healthy 8.2% walk rate. In 2014, Wong established himself as the Cards' primary second baseman with a .249/.292/.388 (.299 wOBA, 90 wRC+) slash line that was right on par for the major-league keystone average of .250/.307/.364 (.298 wOBA, 88 wRC+). Wong hit for a fair amount of power, which helped make up for his lower than average BA and OBP.

Wong walked in just 4.8% of his 2014 major-league PA. The MLB second-base average BB% was 6.8%. The MLB average walk rate overall for non-pitchers was 7.8%. If Wong's plate approach can mature so that he is seeing more pitches and working more walks, he'll become a valuable part of the lineup. His first PA on opening night was heartening as it showed a more mature approach against the lefthanded Lester. It will be interesting to see what Wong's walk rate looks like as the season progresses.

Third Base: Doubles

Matt Carpenter won the 2013 National League Silver Slugger at second base and placed fourth in the MVP voting. Carpenter posted a robust offensive line that year of .318/.392/.481 (.381 wOBA, 146 wRC+) that he was unable to duplicate last season, when he batted .272/.375/.375 (.339 wOBA, 117 wRC+). Carpenter's SLG sagged by 106 points, in part due to a 46-point drop in BA and a lack of power. Carpenter led the league with 55 doubles in 2013, but that total fell to 33 in 2014. Despite his October homer outburst last year, Carpenter is more a gap-power hitter than a dinger hitter, so I'll be keeping tabs on his doubles total this year to see if the more aggressive plate approach discussed early in spring training is manifesting itself in the form of additional power.

Shortstop: BA

The key to Jhonny Peralta's offensive value has typically been batting average (BA). When Peralta's offensive production has fallen below average, his BA has dropped below .260. Last season, Peralta hit for power and worked a lot of walks, which allowed him to be comfortably above average at the plate despite a .263 BA. Nonetheless, Peralta seems unlikely to repeat his .180 ISO (which was his highest since 2008) or his 9.2 BB% (which was higher than any seasonal walk rate since 2007). If his BB% and ISO both sag, Peralta will need an uptick in BA to help counteract (though it likely won't completely offset) such regression.

Left Field: Batting Average on Balls In Play (BABIP)

Matt Holliday hits the ball hard. He has a vicious swing meant to inflict violence on pitched baseballs. It's often successful in doing so. As a result of the scalding hits off Holliday's bat, he's been able to regularly post a BABIP well above the major-league average, which is typically around .300. Holliday's career BABIP is .338. He has only had a BABIP below .322 once and that was last year when Holliday manager just a .298 BABIP, which was below average. As a result, Holliday's BA dropped to career low of .272. Holliday is getting up there in age (2015 is his age-35 season) so his BABIP decline could be the result of the effects of aging. I'll be paying attention to Holliday's BABIP to get an idea of whether this is the case.

Center Field: OBP

Jon Jay had a very good season at the plate in 2014. He hit .303/.372/.378 (.336 wOBA, 112 wRC+). Jay raised his offensive production from 2014, thanks solely to BA. Jay's ISO fell from an already low .095 to .075. Jay also saw his BB% drop from an above-average 8.3% to a well below-average 6.0%. There is more than one way to maintain a high OBP. One is with a high BA; another is with a high BB%. Or you could have a combo of a pretty high BA and BB%. When it comes to Jay in center, I'm not so much interested in the how as the result. Can he maintain an OBP high enough to maintain his offensive value in 2015?

Right Field: wOBA

Weighted On Base Average (wOBA) is a one-stop batting stat that uses linear weights to value the various outcomes a player produces while at the bat. wOBA is scaled to OBP, so that below .290 is awful, .320 is about average, .370 is great, and .400 is excellent. Last season, St. Louis right fielders placed 30th in all of baseball with a .273 wOBA—worse than awful. Jason Heyward owns a career .345 wOBA. Last year, Heyward put up a .329 wOBA, above average but not great. Nonetheless, it would be a tremendous batting upgrade in right field for the Cards. Heyward isn't going to maintain his torrid opening-night batting pace (his wOBA sits at .691 after one game) but it will be fun to see just how much better Heyward makes the Cards in right field this season.

Starting Rotation: IP

The Cards may very well have an innings-pitched problem in the starting rotation. Last year, St. Louis starters totaled 969 1/3 innings pitched (IP), which ranked 16th in MLB. Here are the IP totals ZiPS forecasts for each of the Cardinals' five current starters:

• Adam Wainwright, 203 2/3
• Lance Lynn, 192 2/3
• John Lackey, 175 2/3
• Michael Wacha, 129 1/3
• Carlos Martinez, 150

Bullpen: BB/9

MLB relievers posted a collective 3.29 BB/9 in 2014. Cardinals closer Trevor Rosenthal saw his walk rate increase from 2.39 to 5.37. St. Louis added setup man Jordan Walden, who owns a career 3.91 BB/9 and put up a 4.86 BB/9 a year ago. Then there's Kevin Siegrist, who has posted a career 4.37 BB/9. Sure, there's Seth Maness (1.52 BB/9), Matt Belisle (2.18), and Carlos Villanueva (3.00), but the relievers who seem lined up to work the most high-leverage innings for St. Louis also have pretty high BB/9 capabilities, which could lead to a fair amount of heartburn in Cardinaldom. Consequently, I'll be paying attention to reliever walks this year, especially in high-leverage situations.