After John Farrell was acquired by the Red Sox to be their manager he set to work, as any manager does, to round out his coaching staff. After hiring Juan Nieves to be his pitching coach, he made a statement in an interview that piqued the curiosity of the media. When asked who he was considering for hitting coach, Farrell said that it depends on who the first guy is, but they are looking at hiring two hitting coaches, as that position has evolved over the years into more of a two-person job. There has been a lot of coverage on the subject, as it was being considered to be a radical idea, however there are already six teams in MLB that employ two hitting coaches, with BOS looking to become the 7th.
For years teams have been employing two pitching coaches, having an assistant pitching coach is fairly common these days, using the Red Sox for example, late last season when they fired their lame duck pitching coach they promoted their in-house assistant pitching coach to fill the role for the remainder of the season. For a few seasons now some teams have been adding assistant hitting coaches to the team as well. These assistant coaches aren't listed on the team's roster of coaches, and have to watch the game from the stands as there are MLB rules on the number of coaches allowed in the dugout, but assistants are a trend. Currently, the Tigers (Lloyd McLendon, Toby Harrah), Padres (Phil Plantier, Alonzo Powell), Giants (Hensley Meulens, Joe Lefebvre), Braves (Greg Walker, Scott Fletcher), Phillies (Wally Joyner, Steve Henderson) and Royals (Jack Maloof, Andre David) are the teams with two hitting coaches, and St. Louis is temporarily without a second as Mark McGuire left for LAD, promoting assistant John Mabry to hitting coach. Matheny has said that he will continue the trend set forth there by Tony LaRussa and they will add an assistant hitting coach at some point. Boston isn't exactly breaking the mold by hiring an assistant coach, but they are part of a growing trend.
As Farrell has said in interviews, one of the reasons for an assistant hitting coach is that the job has become more of a two-person job, and there aren't enough hours in the day for one person to be everywhere preforming the duties that a hitting coach should. In Spring Training alone, there are multiple fields, underground cages, and side sessions where hitting is taking place and it is hard for one person to see all of these guys with the grueling schedule Spring Training dictates. During the season, there are cage sessions for each player that the coach needs to be present for, and those sessions eat time away from time he could be meeting with players that need more individualized help, breaking down tape or meeting with the manager to report and discuss various players. In this new role, the assistant is the guy who usually watches each cage session for each player, while the coach handles the other day to day duties. Another possible reason for multiple coaches is that not every player is made for a certain coaches hitting specialty. Some guys are better at getting more power out of guys, some are better at teaching contact and small ball, and some are better at teaching patience and strike zone recognition. Every hitter is different, and a leadoff guy whose skill set is aimed at on base percentage and contact might not get the most he could out of a coach that specializes and focuses on driving the ball and hitting for power. For instance when Keven Seitzer was let go from KC this offseason, part of the reasoning given was that KC was looking for a coach that could help bring out more power from their hitters, they were also looking for guys that had success with young hitters coming up from the minors, even guys that worked directly with those young hitters when they were excelling in the minors. Hosmer, and Moustakas for instance, worked with both of the new hitting coaches they hired in the minors. Maybe it's just a case of the same general philosophy but a different approach to teaching that is required, not every person learns the same way, and that holds true for baseball players.
In PHI, Steve Henderson, formally hitting coach for TB, was hired with the agreement that he would be taking on an assistant hitting coach. Even though the Rays set team records in runs, HR, OBP, and walks, Henderson was let go out of a concern that their team situational hitting wasn't where it should be, anyone who has watched Joe Maddon manage a game completely understands that point. Wally Joyner was brought in as Henderson's assistant exactly for that reason to give a different point of view and get information across in a different way. Phil Plantier, in SD has a philosophy that you have to adapt to the hitter to bring out what they do best, and for him he learned a little bit from everyone he worked with, so the more people to get input from the better. His counterpart, Alonzo Powell spent years overseas in Japan, while he was there he mastered the art of studying and breaking down video, which made him an excellent assistant candidate. The Rays replacement for Steve Henderson, Derek Shelton, earned praise from manager Joe Maddon, who values situational hitting which suits his managing style. Shelton earned the ire of fans however when the team settled into the bottom half of baseball in hitting statistics, and now going into next season, they are considering hiring an assistant for Shelton for many of the reasons listed above.
For years, talk of reuniting pitchers with pitching coaches they had success with has been made when a pitcher struggles under a new regime, and adding assistant coaches to the major league staff allows teams to have the hitting or pitching coach they would like as a team, and also allows a spot for a guy that maybe had success with a young group of the teams hitters or pitchers in the minors, or a guy that specializes with a different type of learner than the main coach does. More variety on a staff means more knowledge to share with players, and more knowledge can't be a bad thing, not to mention having a replacement ready in case a move needs to be made as in the Red Sox case last season or St. Louis this offseason.