Ellis, 31, enjoyed a good season in Oakland last year batting .291 with a .358 on base percentage, but has really struggled in 2011. He currently sits at .217 and a .543 OPS through 62 games played. The Rockies have seen dreadful production this year at second base between Jonathan Herrera, Eric Young, and Chris Nelson and Ellis could potentially provide an upgrade for the remainder of the season. Oakland Coliseum traditionally suppresses offensive output and a move to Coors Field could be the change of scenery that Ellis needs to rebound. He also provides a good glove and should give the infield added defensive prowess.
In exchange, Colorado gave up one of their better right handed relief prospects. Billings converted from a starter in 2010 and has enjoyed some success in the minors. He made his MLB debut earlier this season after the Jorge de la Rosa injury.
With a very weak NL West -- and Colorado struggling to surpass .500 -- Rockies GM Dan O' Dowd had to make a move to escape mediocrity and re-enter contender status. This trade is early enough in the season that Colorado can still pursue a better option at the trade deadline if Ellis doesn't work out; if he does, then the Rockies have become a much better team today.