The two players in the midfield who had the most impact out of the new batch of players this year were probably Martin Rivero and Hendry Thomas. (Jaime Castrillon played as a pseudo-forward so much that he might not count there, plus he had that nagging tendency to have games where he didn't really do anything.)
Priority number one for the Rapids front office this off-season, except perhaps for picking up that designated player forward we keep hearing so much about, should be re-signing the two of them. Rivero was picked up with great difficulty on a loan from Rosario Central, and I have no doubt that if they don't work quickly, he'll be sent right back to Argentinian.
Rivero, at only 23 years old now (Happy birthday by the way, Martin!), was a pick-up for the future. His season in 2012 was frustrating and spotty but full of good moments, just about what you'd expect from a 22-year old playing a difficult position while fighting a language barrier. Whether or not you think he'll improve as the years go along is a matter of opinion, but it'd be tough to never find out by losing him to Rosario Central again.
Thomas belongs to the Rapids for the time being, but was only on a short contract and probably deserves more money for next season if he can pull off a full season of the solid play he put up in his 10 games or so in 2012. Unless Pablo Mastroeni comes back next year, and I'm fully on the 'retire' bandwagon for him, having that settling influence that Thomas brings in the midfield will be a necessity in 2013.