Russell Branyan deal is "Why?" It does not make sense for a team out of a pennant chase to give up younger players for an older one.
There are exceptions though, and we do not have to look very far to find one.
Back in August of 2006, the Mariners traded Jamie Moyer to the Phillies for Andrew Baldwin and Andrew Barb. At the time, the Mariners were clearly out of the race, Moyer was on the wrong side of 40 years old, and Baldwin and Barb were in low levels of the minor leagues. This was a classic trade deadline kind of deal. Presumably, the Phillies were mortgaging small pieces of their future to bolster their 2006 team.
Fast forward to today. Moyer is still with the Phillies, and has been worth roughly 6 WAR for them over his tenure (I am guessing some on how much WAR he provided in 2006 for them, because I can only find his WAR for that entire season). He is now crowding 50, but is still a serviceable pitcher.
Andrew Barb got cut by the Mariners years ago. He never made it out of the low levels of the minors. Andrew Baldwin is in Tacoma for his third season, where he has posted mediocre numbers at best. He is now 27 years old, and is yet to make a major league appearance, or even get on the 40-man roster for that matter.
Oh, and furthermore, the hole left by Moyer in the M's rotation was filled by signing Miguel Batista as a free agent.
Again, the whole point of trading Moyer back then was to gain pieces for the future. However, long-term, Moyer has proven to be significantly better. With the advantage of hindsight, it is easy to see that the Mariners would have been in better shape for the foreseeable future if they had kept around the 40-something southpaw.
I bring this up now because of the Russell Branyan deal. Juan Diaz is totally cut out of the Barb/Baldwin cloth. Ezequiel Carrera is better, but not by leaps and bounds. The trade the Mariners made last night to get Branyan back is constructed similarly to the Moyer deal years ago, except this time around the Mariners are the ones acquiring the veteran.
Now, I just admitted that the M's gave up more in this deal than they acquired with Moyer. Furthermore, Moyer has stayed a serviceable pitcher much longer than I think anyone envisioned. The overwhelming odds are that Branyan does not provide the same kind of production for the Mariners that Moyer has given to the Phillies, and I also think it is likely that Carrera and Diaz provide more value to the Indians than Barb and Baldwin have given the Mariners.
Still, nobody doubts that the Mariners are a better team today than they were yesterday. Sometimes, good players stay good for a little while longer. Often, marginal prospects do not pan out. Branyan could end up impacting the Mariners long term as much as the prospects they gave up could have. We will not have that answer for several years, but the precedent is there.