The Rays had excess starting pitching and did not want to pay Garza $9 million in arbitrated salary. So the Cubs, still believing they could compete, made the deal. Garza's career in Chicago has been average at best. As a Cub, Garza is 15-17. In 2011, his ERA was 3.32 in 31 starts. In 2012, it was 3.91 in 18 starts. His combined WHIP is around 1.211. So maybe he has been an above average starter on an underperforming team.
But most observers don't perceive Garza as the ace of any staff, like they do with Halladay, Verlander or Kershaw.
The Cubs really wanted to exchange Garza's talents for a boatload of prospects at the trading deadline. Garza's value would never be higher, since a contender could have him for this year and all of next year (after arbitration). It was unlikely that the Cubs would have gotten 5 prospects in return, but at least three quality players.
But no trade happened because Garza got hurt. First it was reported as a tricep injury. Then fluid in the arm. Then he took some personal time for the birth of his child. The Cubs said he would make a start just before the trade deadline, but that did not come to pass. Now, the word is Garza is on the DL with a "stress reaction," which is just short of a stress fracture in his elbow at the triceps. Blake Parker has a similar injury, and he has been out since June 1st. So that means Garza is done for 2012. That means Garza will not competitively pitch until spring training 2013. That means he won't be traded this off-season. That means his trade value is falling to near zero.
Timing is everything, especially in baseball. If the Cubs, knowing that the team was going to be in the bottom all season, should have tried to deal Garza in June, not July. But they held on to him to juice up the bidding near the deadline. But that strategy backfired.
The diplomatic word from Clark and Addison is that the front office is happy to have Garza in the rotation in 2013. They have no choice in the matter. Garza will probably get a good raise in his final year of arbitration to $10.5 to $11.25 million, numbers that can't make the business side of the Cubs happy since it has been all about cutting payroll for 2013.
The fallout of this saga is that the Cubs are stuck with a starting pitcher that does not fit into their plans (rebuilding) or their budget for 2013, and may be difficult to trade because of his injury history.