A little more than eight years ago, the Seattle Mariners traded Carlos Guillen to the Detroit Tigers for Ramon Santiago and minor league infielder Juan Gonzalez. While Santiago settled in as a utility man and Gonzalez never reached the majors, Guillen made three All-Star teams, posted a 127 OPS+ and averaged about 3.7 Baseball-Reference Wins Above Replacement for Detroit from 2004-2008.
The last three seasons of Guillen's four-year, $48 million extension with the Tigers went sour, however. He had a 95 OPS+ and averaged just 0.3 WAR while limited by shoulder, hamstring, calf, wrist injuries, plus a left knee problem that culminated in microfracture surgery in September of 2010. And now, the hobbled 36-year-old returns to Seattle on a minor league contract, hoping his body is mended enough to compete for playing time at third base and in the outfield on an offensively-starved M's squad.
The switch-hitter's various afflictions have taken a toll on his secondary skills. Guillen's walk rate has declined from 11.9% in 2009 to 7.6% in 2010 and 4.9% last year, while his slugging percentage dipped from .419 in 2009-2010 to .368 in very limited time in 2011.
Guillen has become more impatient at the plate, chasing nearly 30% of pitches out of the zone since '09 (he chased 24% in 2008). He has extended his zone vertically, swinging at more would-be balls below the knees:
Aside from the more hack-happy approach, Guillen just didn't hit the ball with as much authority after returning from microfracture surgery and then succumbing to a wrist problem. His fly balls traveled an average distance of 262 feet in 2011, down from 283 feet in 2010 and 280 feet in 2009.
There's no harm in seeing if Guillen can recapture some semblance of the switch-hitting goodness he provided in Detroit, but odds are the M's traded him too early and brought him back too late to enjoy the productive years of his career.