Why Xander Bogaerts is the key to the Red Sox season

As the Boston Red Sox open the 2015 season against the Philadelphia Phillies, all eyes will be on their revamped lineup and starting rotation. Hanley Ramírez, Pablo Sandoval, Rick Porcello and Justin Masterson are just a few high-priced players (combined salary close to $60 million this season) acquired in the offseason to help the Red Sox try to bounce back from a last-place finish in 2014.

Although the Red Sox’s additions should make a significant impact, one key to Boston’s success is 22-year-old shortstop Xander Bogaerts, for three reasons listed below.

Defense, defense, defense

The Red Sox rotation was revamped, but the three additions have one thing in common: groundballs. All five projected starters ranked in the top half of the league in groundball rate last season, including four (Masterson, Joe Kelly, Wade Miley and Porcello) who induced a groundball on more than half of their opponents’ balls in play.

On more than 38 percent of each of their grounders, the ball was put in play toward the shortstop or up the middle. That means that, on average, about one in five balls in play against the Red Sox starters are projected to be ground balls in the direction of Bogaerts.

In 2014, Bogaerts split his time between shortstop and third base, but defense was not a strongpoint at either position. Among 35 players with at least 500 innings at shortstop, Bogaerts ranked 28th in defensive runs saved, and among the 38 players with 300 innings at third, he ranked 34th in defensive runs saved. Overall, Bogaerts cost the Red Sox about one win last season because of his below-average defense.

One of the biggest issues for Bogaerts at shortstop was turning double plays. Among those 35 shortstops with 500 innings, the only player worse than Bogaerts at turning double plays was Everth Cabrera, according to Fangraphs’ double-play runs saved (rGDP) metric.

With the increased ground balls projected to result from the Red Sox's new rotation, Bogaerts’ defensive development will be a key to Boston's season.

Bottom-of-the-order production

After hitting in a variety of spots last season, Bogaerts is projected to hit eighth this year. Last year, the top four players in the Red Sox order produced (third in the American League in OBP), but the bottom of the order was a momentum stopper. No AL team had a lower weighted on-base average from its seven through nine hitters than the Red Sox (.270). Weighted on-base average (wOBA) is a catch-all offensive metric that weighs all aspects of at-bats (getting base hits, drawing walks, getting hit by pitches, etc.) to measure a hitter’s overall value.

With rookie Rusney Castillo and Ryan Hanigan also projected to hit at the bottom of the order (when Castillo is called up), the Red Sox need increased offensive production from Bogaerts. That means that Bogaerts must fix his weakness: breaking balls. Last season, in 158 plate appearances that ended in a breaking ball, he had a .147 batting average and missed on 35 percent of his swings. Among the 200 players with at least 100 such plate appearances, he had the eighth-worst batting average and second-worst slugging percentage, behind teammate Jackie Bradley Jr.

Lack of a backup plan

According to ZiPS projections, Bogaerts’ projected WAR of 2.5 ranks seventh on the Red Sox. If he is unable to live up to expectations, Boston’s backup plans at shortstop include moving Ramírez back to the infield, starting Brock Holt at shortstop or calling up Triple-A shortstop Deven Marrero.

None of those options would provide the value that Bogaerts is expected to produce. Ramírez has regressed considerably as a fielder, and he was worse than Bogaerts at shortstop last season. Holt, despite playing shortstop in college, has minimal experience (12 games) there since he entered the league and at times struggled to field that position. Finally, Marrero hit .210 for Triple-A Pawtucket last season and is not ready to hit in the big leagues.

If Bogaerts can live up to expectations, the Red Sox have a great chance to go from worst to first...again.