The scouting report on David Ortiz is that he is going to pull the ball, and often times pull it hard. This is the reason so many teams have instituted the over shift when facing the left-handed slugger. For years it worked, but in the winter going into the 2011 season, the Red Sox acquire the left hander with one of the smoothest opposite field strokes in the game, Adrian Gonzalez. Since that acquisition, Ortiz and AGonz have made fast friends, sharing hitting advice, and it is definitely showing.
From 2008-2010, Ortiz had only 104 hits to the opposite field with only 12 home runs and a .578 slugging percentage. Below is the spread for Ortiz opposite field production over those years (production is indicated in slugging percentage).
In contrast, Gonzalez crushed pitchers to the opposite side with 160 hits, 48 home runs, and an .809 slugging percentage. Gonzalez could take almost any pitch on the outside half and give it a ride.
Since Gonzalez arrived, Ortiz has seen a rebirth to his opposite field hitting ability, which should cause some teams to be wary of the Red Sox slugger. After a full season as teammates, Ortiz is off to the hottest April he has had in years. He is hitting a robust .444 average and .714 slugging percentage while spreading the ball around the whole field.
Also, over the course of 2008-2010, Ortiz hit an abysmal .218 versus left handed pitching, mustering up a less than impressive .383 slugging percentage. His ability to put the ball in play was horrible, leading to his removal from games facing lefties and contributing to some of Ortiz's slowest starts in his career.
Post-2011, Ortiz has been on a torrid pace, hitting lefites at a .340/.567 clip. Being able to go with the breaking ball and outside pitches to the opposite field has corrected Ortiz's swing and made him a dangerous middle of the order hitter for the Red Sox again.