The Cubs roster is largely set at this point. The Cubs have five infielders virtually locked in with Luis Valbuena, Donnie Murphy, Starlin Castro, Darwin Barney, and Anthony Rizzo. The outfield has fourth players pretty much set with Nate Schierholtz, Ryan Sweeney, Justin Ruggiano, and Junior Lake. Adding the two catchers brings the Cubs roster to 11 players. Emilio Bonifacio seems likely to nab a bench spot at the moment. That means there is one spot left for position players. The formula might change if Mike Olt grabs a spot making Donnie Murphy potentially redundant. Or perhaps injury strikes a player down and opens another spot. As is though there is one slot open right now.
Bonifacio making the team allows some flexibility in who they choose for that last spot, but there is normally five outfielders on a roster. There are plenty of options for the fifth outfielder spot in Casper Wells, Ryan Kalish, Darnell McDonald, Mitch Maier, etc. However, Chris Coghlan might be the most interesting choice. Coghlan was Rookie of the Year in 2009 beating out Andrew McCutchen for the award. Since that stellar 2009 season, he has yet to be able to post an above average offensive season. His slash line since that Rookie of the Year campaign has been .242/.307/.352 with an OPS+ of 79. That is simply dreadful and rather amazing when you consider his 2009 slash line produced .321/.390/.460 with a 127 OPS+.
So what happened to Coghlan? Is Coghlan a one year wonder that was simply lucky? Did the league figure him out? Looking at his 2009 season his BABIP was a jaw dropping .365, and ever since then has been .289. Batter BABIP is difficult to figure out what is luck and what is skill. The batter has far more control over converting batted balls into hits then the pitcher does it seems. The other concerning aspect of the situation is that Coghlan's plate discipline skills seemed to decline rapidly as well. After posting similar BB% (9.4%) and K% (13.6%) to his minor league career in 2009, his rates have decline to 8.0% and 18.5%. This does suggest the league figuring out Coghlan to some degree, but also suggests that his 2009 wasn't entirely luck driven.
The other part of the story with Chris Coghlan is injury. Coghaln lost the rest of his 2010 campaign due to a knee injury and has yet to play a full season ever since. The Cubs bench coach is familiar with Coghlan, and that perhaps gives Coghlan an advantage for landing the fifth outfielder spot. The other advantage Coghlan might have is that his true healthy talent level might be much higher than he has shown in the past several seasons. One piece of objective data that points to this is the power decline that Coghlan has suffered from since the injury. His ISO prior to suffering the knee injury was .129 and after the injury it has been .108.
Coghlan simply was not hitting the ball as far as he was prior to the injury. In 2009 and 2010, Coghlan's home runs and fly balls had an average distance of 287.2 which around the same distance of Anthony Rizzo for comparison's sake. Here is the data in graphic form:
The questions remain of how much of that decline was related to injury and is Coghlan healthy now. But there is reason to believe that the Rookie of the Year season was not a complete mirage. Coghlan might be an intriguing candidate to make the team. If he is a surprise the Cubs have control over Coghlan through 2016, and might provide an interesting stopgap until the outfield prospects are ready.