People thought Dombrowski was going to break the bank for Shin Soo Choo. I'll admit, he's a very good player. He had 712 plate appearances last year at a .285/.423/.462 clip (AVG/OBP/SLG). But, that was his second best offensive season, he has had injuries in his career, and he turns 32 in July. Outfielders tend not to age well (outside of Barry Bonds, who may or may have not been taking illegal substances) and several have severely underperformed after signing big free agent contracts. Please see Josh Hamilton, Carl Crawford, and BJ Upton for more information.
So now we have Dirks and Davis Platooning in Left Field. Dirks has career splits of .265/.328/.393 vs. Lefties and .278/.333/.418 vs. Righties. Davis has career splits of .294/.354/.425 vs. Lefties and .256/.297/.354 vs. Righties. Say Dirks plays 2/3 of the games and Davis plays 1/3 (Generally more Righties than Lefties). Then, say Dirks gets 85% of his plate appereances (referred to as PAs from here on) against Righties and 15% against Lefties (Ideally you would want 100% of your ABs to have the right/lefty advantage but this is where bullpens and injuries come into play. For the estimate of 85%, I used how the Red Sox used Mike Carp last year who had 26 PAs vs. LHP and 190 vs. RHP) . The opposite would apply to Davis. With that composite, you would end up with a platoon player who hits .280/.337/.414.
In addition, Shin Soo Choo is not a good defender by any means. Many point out to the fact that he is overmatched playing center field and could actually be a pretty good corner outfielder. That said, Dirks nor Davis are not Willie Mays in the outfield but have shown more promise than Choo. Overall, I would call our current platoon average defensively and Choo below average.
The other part of the game is Speed. Despite stealing 21 and 20 bases each of the last 2 years, Choo actually has been a below average base runner. He has been an above baserunner in the past, but again, it's not likely something to improve as he continues to age. Contrary to popular belief, baserunning is not solely dictated by how many bases you steal. It is also determined by how many times you get thrown out, picked off, or take an extra base on a base hit (i.e. going first to third on a single, scoring from 1st on a double, etc.). On the other hand, Dirks was one of the few above average baserunners for the Tigers last year (The only other player with more than 275 PAs who was better was Austin Jackson). He is only 27 so we can expect him to be above average again. Davis, who only had 360 PAs last year, still had the second most value for ANY player in MLB (Jacoby Ellsbury was first) from a baserunning standpoint. The value he generated on the the bases in half a season would more than offset the lack of value of full seasons from both Prince Fielder and Miguel Cabrera COMBINED (10.2 vs. -9.7).
Juan Pierre is 36 and is still a fantastic baserunner (26th most baserunning value in only 330 PAs).
Choo just signed for 7 years and $130 million. Davis signed for 2 years, $10 million. Dirks is at the league minimum. Choo is a better player. He offers about an extra 100 to 125 points better OPS over our current platoon. That said, Dirks/Davis are slightly better defensively and much better at baserunning. Our platoon starts to look like Desmond Jennings of Tampa Bay. Last year in 602 PAs, he hit .252/.334/.414 with average defense, and good baserunning. He was worth 3.2 wins above replacement (WAR) last year. If you prorated it to the number of PAs Choo got last year (602 vs. 712), Jennings would have been worth 3.8 WAR last year. Choo is unlikely to repeat his amazing performance from a year ago and is currently forecasted to be worth 3.2 and 4.8 WAR this year.
Lastly, if we signed Choo (who did not sign his qualifying offer), we would be sacrificing our top pick in next year's amateur draft. First round picks are very important in this league and exceedingly valuable to the Tigers who have one of the most depleted farm systems in all of MLB. We only have one prospect in the top 100 (Castellanos) that is a product of several trades and sacrificing picks for free agent signings.
Is all of this worth an extra $120 million? I don't think so. Apparently neither does Dombrowski.