Before Alfonso Soriano was traded for Alex Rodriguez, the second baseman hit .290/.338/.525 for a .365 wOBA and a 124 wRC+ in his last season with the Yankees. In 2013, in his 243 plate appearances with the Bombers, Soriano hit .256/.325/.525 with a .366 wOBA and 130 wRC+. The right-handed hitter has lost some of his ability to hit for contact, but his power hasn't gone away. The 17 home runs he hit in the second half of 2013 played a huge factor in the Yankees' potential comeback in the AL East race.
Soriano worked out well in 2013, but his upcoming 2014 performance could bring some regression. There were no numbers that were startlingly out of the ordinary, but his power did increase substantially. When a power hitter moves from Wrigley Field to Yankee Stadium, this sort of thing happens. Soriano, who hits for power to all fields, benefitted greatly in the AL East and their hitter-friendly ballparks.
His type of power in Yankee Stadium is sustainable. If you take a larger sample size of hits from Wrigley Field, in this case from 2012, you'll see that he still would have benefitted from playing in the Bronx.
Camden Yards, the Rogers Center, and Fenway are also hitter friendly ballparks, while Tropicana is considered home run neutral. Fenway should especially benefit Soriano, as we'll again take his hits from home in 2012 and put them on the map of Fenway park.
Though some of these were likely line drives that would have gone for doubles off the Green Monster, Soriano has 29 hits in home run territory. This is from his home games At Wrigley Field alone in 2012.
The other ballparks don't have as dramatic of an effect, but there is still some benefit. Altogether, the Yankees will play 108 games between these four ballparks (Yankee Stadium, Fenway, Camden Yards, and the Rogers Center). This doesn't include other homestands against other hitter-friendly matchups like the Rangers, White Sox, Brewers, and even the season opener against the Astros. That's 120 games in hitter-friendly ballparks for Soriano, as opposed to the more difficult parks in the NL Central, with the exception of Great American Ballpark and Miller Park.
Soriano's power numbers should continue to inflate, even as he enters his age 38 season. The biggest problem he may deal with is his recent increase in strikeouts and declining batting average on ground balls. His swing-hard style plays well into hitting hard line drives and fly balls, but it also leads to hard choppers in the infield and less contact. Though he cut down on his swing rates outside of the strike zone with the Yankees in 2013, his contact rate dropped from around 74% to 69%. This combination of decline in contact and speed, could manifest in decline of his batting average.
There is some optimism though, as Soriano looked faster in 2013. From 2007 through 2012, Soriano dealt with substantial leg issues that sapped his speed. He went on the disabled list three times for knee surgery and two quadricep strains. He's also seen some significant time missed sporadically for wear and tear on his legs. In 2013, Soriano missed just one day due to injury, and that was for spraining his thumb. For the first time since 2008, Soriano stole 18 bases in 2013, and his defense was well rated by by UZR (7.0), RZR (.929), and even DRS gave him 1 run saved.
If Soriano survives leg issues in his age 38 season, his batting average on ground balls should increase and help his overall batting average. His strikeout rates will probably continue to be high, but that's the price you pay for such hard contact. Assuming his legs stay relatively healthy, which they should with additional time off as the designated hitter, I'll give him a slash of .255/.310/.510 with 35 home runs.