Receiving the call to the Rockies are two pitchers (Jhoulys Chacin and Matt Belisle) and two hitters (Matt Murton and Mike McCoy). All of the players except for McCoy have played for the Rockies this season.
To make room for Belisle and McCoy (Murton and Chacin were already on the 40 man roster), the Rockies designated Adam Eaton for assignment and placed Chris Nelson on the 60 day DL.
These moves provide much needed depth for the stretch run to the Rockies, who have suffered a recent rash of injuries to key players.
Speaking of that, here's an injury update by the AP on Troy Tulowitzki and Ian Stewart.