That sounds a little low. Best comparable recently mid season would be Lee (and Mark Lowe) to the Rangers, I think. Smoak was a starting 1b called up that year and highly regarded, Blake Beavan was a 21 year old AA arm regarded as as #4 starter innings eater, Josh Leuke, and a mystery 2d baseman. Per BA:
Holding the most coveted trade chip at this year's deadline, the Mariners cashed in lefthander Cliff Lee a little early, sending him to the Rangers for young first baseman Justin Smoak and three prospects. Texas also receives 27-year-old reliever Mark Lowe, a righthander (and University of Texas-Arlington product) who is slated to miss the rest of the season after having back surgery.
Also headed to Seattle are a trio of players from the Double-A Frisco roster: righthanders Blake Beavan, a Rangers' first-round pick in 2007, and Josh Lueke as well as second baseman Matt Lawson. The Mariners also furnished the Rangers with approximately $2.5 million to help the financially-strapped club cover the remainder of Lee's $8 million salary, which works out to roughly $4.2 million.
I think in 2008 there was the CC trade to the Brewers. what you need is one high minors / major league well regarded lock (LaPorta, Smoak), and at least one other likely major league rotation piece (Beavan) or prospect with upside (Brantley), plus some other pieces who might play (Leuke, Zach Jackson).
Just a guess - Rosenbaum would be the Beavan piece, Espinosa or Lombo would be the regular / prospect, then add something who might be a contributor.