Two spots on the roster opened Monday, when Kyle Lohse and Lance Berkman officially entered free agency. Rondon took one of those vacancies, with the other now occupied by right-hander Kyle McClellan, who had to come off the 60-day disabled list.
As a result, the Cardinals' 40-man roster is currently full. There are certain to be additional roster changes before Nov. 20, the deadline for teams to protect players otherwise eligible to be taken in December's Rule 5 Draft.
Rondon, who is currently pitching in the Venezuelan Winter League, split the 2012 season between Double-A Springfield and Triple-A Memphis. The 24-year-old righty posted a combined 3.49 ERA in 46 appearances. He struck out 50 and walked 24 in 49 innings. Opponents hit .230 off Rondon.
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.