First, no body trades away their ACE pitcher unless they are rebuilding, which the Mariners clearly are NOT doing. If ANY team is serious about making a run after the All-Star break, then, they will wait for the sellers/rebuilders to offer up their soon-to-be free agents for a couplpe of prospects.
Here is a list of expected free agents for 2015:
http://www.mlbtraderumors.com/2013/0...ee-agents.html
Now this list could apply to any team in baseball but we'll focus on Seattle who needs to improve at all but one position, and that's second base.
At shortstop: Any Marlin is available at the right price and (if healthy) Furcal could be an upgrade at a cheap price. The oft injured Jose Reyes and Jimmy Rollins, while not up for free agency could be significant trading blocks this year given the trajectory of their teams, and both seem to have a contract worthy of dumping into someone elses lap.
Third Base: Welcome HOME A-Rod, however, NOBODY is that stupid, right? The best option could be Chase Headley in San Diego.
First base: Outside of second base, this is your only other position where you have two solid players on staff in Smoak and Hart, Adam LaRoche, if not too busy grooming his beard to be a 30+ homerun hitter again could be there for sure! Cuddyer is the best option of all, but likely would have to pay a hefty price.
Outfield: So many options here, but, if you were to bring back A-rod, why not Ichiro? The better options would be Nelson Cruz, if the orioles are cruising at the bottom come break time. Markakis alternatively. Granderson doesnt seem to be so popular these days with his new contract in New York so he could be on the block as well.
I would definitely not trade away your best player and face of the franchise to get any 1 or 2 of these guys. Believe me, no one is giving away their .300, 30 HR, 100 RBI guy unless the contracts running out and they know re-signing is unlikely. The risk is having to give up your unproven young talent from the minors, which seeems to work for a lot of teams anyway.