By most accounts, the Tigers were one of the weaker defensive teams in baseball last year, especially in the first half. If you couldn't tell by observation, the statistics told the story as they finished near the bottom of Major League Baseball in all advanced team defensive metrics. They have made moves in the past 12 months to shore up their defense swapping out Ryan Raburn, Delmon Young and Brennan Boesch for Omar Infante, Andy Dirks and Torii Hunter.
Early this season, the new defensive alignment appeared to be working, at least based on observation. In recent weeks, however, they seem to have reverted to their poor form of the first half of 2012. Other than Infante, the infield is still greatly lacking in range and Hunter appears to have slowed down a step in right field. So, it appears the only above average defenders are Infante and center fielder Austin Jackson. Individual defense is difficult to measure at this point in the season, but team defense can be gauged reasonably well now and that will be my focus here.
If you just look at errors, then there does not seem to be a problem. The Tigers Fielding Percentage - the proportion of total plays ( putouts, assists and errors) which result in a putout or an assist - is .989 which is fifth best in the majors and up from .983 last year. Fielding Percentage is a reasonable measure of sure-handedness, but it is not a complete measure of defense. It penalizes players for their errors, but fails to dock them for balls they could not reach. This is a problem because not getting to playable ball is generally as costly as making an error.
A better measure of overall team fielding is Defensive Efficiency Ratio (DER), first introduced by Bill James in the 1978 Baseball Abstract. The DER metric is the percentage of batted balls in play, not including home runs, which are converted to outs by a team's fielders. The Tigers have converted 69.1% (.691 DER) of batted balls in play into outs which is 29th in the majors. Only the Twins are worse at .685.
It is easier to turn a batted ball in play into an out in some parks than others, so Baseball Prospectus adjusts DER for ballpark with Park Adjusted Defensive Efficiency (PADE). The Tigers PADE is -1.89 which says that they have been 1.89% worse at turning batted balls into outs than the average team. That might not sound like a lot, but each percentage point is worth about 13 runs meaning that fielding has cost the team an estimated 25 runs above average. They rank 28th in the majors on that statistic.
An alternative to DER/PADE is Total Zone Fielding Runs (Rtot) found at Baseball-Reference. Developed by analyst Sean Smith, Total Zone considers the following: plays made, errors, batted ball type, handedness of pitcher and batter and park adjustments. Plays made above average are calculated and converted to runs using situational run expectancies. The Tigers are 35 Total Zone Fielding Runs below average which is worst in the majors.
One more option is Defensive Runs Saved (DRS) created by John Dewan at Baseball Info Solutions (BIS).
Using detailed play-by-play data recorded by BIS video scouts, this system breaks
the field into small areas and determines the probabilities of players making
plays in each area of the field based on location, speed (hard, medium, soft)
and batted ball type (ground ball, fly ball, line drive, bunt). The system uses these probabilities to
determine how many plays each player was expected to make and how many he actually
did make in comparison to the average player.
Plays made are then converted to defensive runs above average. The Tigers have a DRS of 11 runs worse than average which is 21st in MLB.
So, the three defensive metrics do not agree on the number of runs fielding has cost the Tigers, they all say the Tigers are in the bottom third of the majors defensively once again this year. The Tigers are built around immobile sluggers, so there is not much more that can be done to help the defense at this time. Fortunately, they generally have enough hitting and starting pitching to overcome their defensive failings. At times, when the hitting or pitching is not clicking though, the poor defense becomes quite noticeable.