If we go by the number of rumors flying around in the past two months about DeRosa, there were many other clubs besides the Cardinals who were interested in DeRosa. Because he can play five positions at least adequately (first, second, third, left and right), has been a very good offensive player for four years running, and has a rep for being good in the clubhouse, it's not surprising that many teams saw him as being the missing piece to their lineup. DeRosa is also a free agent at the end of this season, and would cost his new team about $3.0M in salary between now and September. So when the Indians finally fell out of contention after losing six straight games, the only question was when they'd be trading DeRosa, since they'd be getting a good return. I don't really think at this point the Indians got the return they could have gotten, though there's still the PTBNL to come.
For the Cardinals, who need help at both second and third, not to mention at the plate, DeRosa is an excellent fit. They were also willing to part with a major-league player, one that not only would help the Indians immediately in an area of desperate need (the bullpen), but also had less than one season of service time, and who wouldn't be eligible for arbitration until at least after the 2010 season. The PTBNL, noted by Mark Shapiro as an "important piece", is most likely a good minor-league prospect.
Chris Perez was drafted by the Cardindals in the Sandwich Round of the 2006 Draft (42nd pick overall). He was a reliever for the University of Miami, so he didn't have to go through the minor-league transition that college starters have to go through to become major-league relievers. He moved quickly, starting in Low-A after signing in 2006, then starting in AA and ending in AAA in 2007, and getting to the majors in 2008. At all levels, he's had great strikeout ratios (minor-league 12.0/9IP), great hit ratios (4.8/9IP), and horrid walk ratios (6.0/9IP). Those numbers have come with him to the majors, for in 62.1 innings with the Cardinals, he's struck out 72, given up 51 hits, and walked 37.
Stuff-wise, Perez sports two pitches: a mid-90s fastball with movement, and a slider. Both pitches are considered out pitches in the majors. The problem for Perez is staying in the strike zone, something that separates the Joe Nathans of the world from the Jason Davises and Fernando Cabreras. The Indians' coaching staff has some work ahead of them to turn Perez from a pitcher with a lot of potential to a late-inning stalwart. Given the recent track of relievers in this organization, I'm pretty skeptical that he'll make that transition in Cleveland.
SBN's Driveline Mechanics notes some problems with his mechanics:
A Mechanical Look at Chris Perez - Driveline Mechanics
Needless to say, I'm not enthused with this arm action. It often causes lateral displacement of the pitching arm and subsequently represents a timing flaw, since the arm needs to get from this displaced position to the high-cocked position quickly. In doing so, this causes the pitching forearm to lay back violently in shoulder external rotation, and while the result may create a higher value of Maximum External Rotation (MER) and thusly higher velocity, it is also the cause of "Late Forearm Turnover" which places a significantly high load on the ulnar collateral ligament.
So the same mechanical problems that are causing his wildness also indicates an elevated risk of arm injury. He's a high-risk/high-reward reliever; he could be the Indians' closer for the next 4-5 years, he could flame out quickly, or he could spend a lot of time on the Disabled List. I think the latter two outcomes are more likely.
It's too early to make a final judgment on this trade because one half of the return isn't known yet, but thus far I don't think the Indians got the kind of return that they could have. From a roster standpoint, this was the right time to deal DeRosa, for Asdrubal Cabrera will be activated today, and the Indians would like to see what Matt LaPorta and/or Michael Brantley can do in the majors. But I wonder if the Indians could have driven up the price for DeRosa had they held onto him for another week or two.