Soriano is Mr. May

At the time Alfonso Soriano signed his eight-year $136 million dollar contract in November of 2006, it was the fifth-largest contract given to a major league player. Behind such stalwarts as Alex Rodriguez ($252 million / 10 years), Derek Jeter ($189 million / 10 years), Manny Ramirez ($160 million / 8 years) and Todd Helton ($141.5 million / 11 years), Soriano was expected to be a key centerpiece for a team that had finished dead last in the National League (2006: 66-96).
To say that Soriano’s arrival in the Windy City has been a mixed-bag is quite an understatement. In between all-star selections in 2007 and 2008, Soriano has also spent considerable time on the disabled list and his been chided for his defensive lapses and base running gaffes. Cubs fans either love him or hate him, depending on the day.
One thing Cubs fans have to agree on though: He owns the month of May.

In his career, Soriano has more hits (304), runs (183), RBI (171), stolen bases (51) and home runs (66) than in any other month in his career. While no longer much of a threat on the basepaths (19 steals in a season is his Cubs high), Soriano has continued to have success in the power department, hitting the eighth most home runs (24) of any Major Leaguer in the month of May since 2007.

April Showers bring May Power

Alfonso Soriano: 2007-2010

As noted in the chart above, Soriano has dominated opposing pitchers fastballs. Not only is Soriano hitting .352 against the fastball since 2007, but 55 of his 90 career home runs as a Cub have come off of the fastball, including four of his five home runs this May.
A look at Soriano’s numbers by pitch-type further indicates his dominance against the fastball in May.

May 2007-2010

One of the key components to Soriano’s success in May, aside from his ability to neither chase nor miss the fastball, has been his consistency. In 100 career games in May as Cub, Soriano has had a base hit in 80 of them. Impressive in and of itself, Soriano further adds to his month of dominance by collecting multiple base hits in 34 of those games and never going more than two games without a hit.
While the Cubs have not performed to the level that most envisioned so far, much of the blame cannot be put on the shoulders of Alfonso Soriano (at least offensively).